Multilingual Demographic Dictionary

unified second edition, English volume
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Table of contents



The first edition

In 1953, the Population Commission of the United Nations requested the preparation of a Multilingual Demographic Dictionary, a task in which the International Union for the Scientific Study of Population (IUSSP) offered to collaborate. In 1955, an ad hoc Committee under the chairmanship of P. Vincent of France was established to prepare the English, French and Spanish versions of the Dictionary. The Committee included as members: C.E. Dieulefait (Argentina), H.F. Dorn (United States), E. Grebenik (United Kingdom), P. Luzzato-Fegiz (Italy), M. Pascua (Switzerland) and J. Ros Jimeno (Spain). The French and English versions of the Dictionary were published in 1958 and the Spanish version in 1959. Versions in ten other languages appeared between that date and 1971.

The second edition

Because of the rapid development of demography and population studies during the 1960s, in 1969 the Population Commission recommended the updating of the Multilingual Demographic Dictionary, a task that was pursued once more in collaboration with IUSSP. A new Committee on International Demographic Terminology was set up under the chairmanship of P. Paillat (France) and started work in 1972 with financial support from the U.S. Bureau of the Census. Other members of the Committee were: A. Boyarski (USSR), E. Grebenik (United Kingdom), K. Mayer (Switzerland), J. Nadal (Spain) and S. Kono (Japan). The Committee submitted a revised draft to the consideration of a hundred or so demographic centres that provided comments. In 1976, Prof. Louis Henry was commissioned by IUSSP to edit the work and produce the second edition of the Dictionary in French. IUSSP then requested Prof. Etienne van de Walle to adapt and translate the French second edition into English. The second edition in English was published in 1982. Eventually, the second edition would be issued in all official languages of the United Nations.

From the second edition to Demopædia

The series of Multilingual Demographic Dictionaries is one of the most enduring products in the history of demography and one of the most fruitful thanks to the work and engagement of scholars who have translated the original French or English versions into their own languages. As a result of those efforts, the international community can benefit today from access to 14 language versions of the second edition of the Demographic Dictionary, mainly thanks to the initiative undertaken by Nicolas Brouard in compiling the out-of-print versions of the Dictionaries in different languages and developing a Wiki-based presentation of all of them as a web-accessible Multilingual Demographic Dictionary. The United Nations Population Division, IUSSP and the Comité national français of the IUSSP have all supported this work in order to facilitate access to these valuable reference texts.

Why on-line?

Because the Demographic Dictionaries in various languages were conceived as tools to serve people in many countries, making them accessible via the Internet was thought mandatory. Today, thanks to the project led by Nicolas Brouard, standard demographic terminology and its meaning is only two clicks away for students, teachers, professors, researchers, government officials, journalists, non-governmental organizations and the public at large, all working in their own languages.


Visitors to Demopædia can consult the different language modules, read them, or download and print them. All copyright owners have made this possible. Users can search for a demographic term, surf between linked terms and expressions, or switch to another language or edition. Because each Dictionary consists of thematic chapters, terms are located in context, providing not only a definition of each term but also an understanding of the subject matter for which a term is relevant. Each language module has a built-in index that facilitates navigation and cross-referencing. In addition, the Wiki platform provides powerful tools for further development. It is envisaged that the next stage of the project will allow specialists to post additions, revisions or corrections to the second edition.

What is next?

Demographic knowledge made huge advances since the last editions of the Dictionary have been published. There is a clear sense that the structure and texts need updating. Doing it in a traditional format of ’live’ panels and working groups would be hardly feasible. Developing on-line a renewed edition of multilingual encyclopedic demographic dictionary should be efficient and will unleash the potential of wide cooperation of professionals. Demopædia will host this project.

Demopædia also has the potential to become a platform for sharing and building a wider knowledge base in demography and population studies. Our vision is an extensive and constantly evolving encyclopedia on population, serving the world community and benefiting from influxes of ideas and texts.

For an unified second edition of the dictionaries as an intermediate step

Since the training in Marrakech, a lot of work has been done to improve the quality of the scanned texts. Specific computer programs using parsers have cross check the texts of the first and second editions in about 12 to 13 languages in order to detect the missing text terms in one or another language.

The first analysis of this work reveals that the second edition is not as rigorous as the first was. The first edition was the result of the Commission on terminology during the mid 50’s, but the second was first revised in French in 1981 and translated and adapted to English in 1982 and in Spanish in 1985, German in 1987 etc. up to Czech in 2005.

Some terms, expressions and even complete paragraphs have not been translated into English, but in Spanish, Arabic, German etc.. And a few sentences and paragraphs have been added into the English second edition but never translated into the French second edition which was already published. Also the Spanish second edition added a few new text terms which are not translated into any other language but Arabic.

The German second edition (1987) defined a lot of more modern text terms which haven’t been translated in any other language.

Editions, published after 1987, did not add any new term and thus a natural limit is 1987 (German) but harmonization between the three languages of the IUSSP could be an important step.

In many language specific editions, the numbering of the text terms differed (even between French and English) most of times due to errors but sometimes because a text term was not translated. The advantage of the technical work is to highlight the missing text terms in order to decide if the word is not used in this language or if it is an omission.


Preface of the first edition (1958)

At its fourth session the Population Commission of the United Nations requested the Secretary-General to include the preparation of a multilingual demographic dictionary in the Secretariat’s work programme. Several months later the International Union for the Scientific Study of Population, at its General Assembly in Geneva, offered to collaborate with the United Nations in this project and set up a sub-committee to prepare a plan of work. At the fifth session of the Population Commission the Secretary-General was asked to accept the Union’s offer, and the Dictionary Committee was given the task of drafting versions of the dictionary in English, French and Spanish.

The primary purpose of the dictionary is to serve as a useful tool for technical translation. It consists of separate sections, each of which presents in one language the technical terms used in demography; the text is followed by an alphabetical index of terms. The texts in, the various languages correspond to one another, and equivalent terms in different languages have the same reference number so that it is possible to identify them in the different volumes. The Committee entrusted with the task of preparing the three initial volumes consisted of:

The first draft consisted of a basic French text which was prepared in the Institut national d’études demographiques in France under the general supervision of M. Vincent. This text was translated into English and Spanish by Messrs. Grebenik and Ros Jimeno respectively. The draft bad to be completed somewhat hurriedly in view of the approach of the World Population Conference, at which participants received a provisional edition, dated June 1954, published by the United Nations. The dissemination of this provisional edition made it possible for a number of experts to comment critically on the draft and gave the Committee an opportunity to take account of the comments received. Some of the imperfections of the first draft were due to the fact that the basic text had been prepared in a single language only—French. It was clear that considerable differences existed between the terminologies in English and in the Romance languages, and that a compromise between different conceptions was essential. It was further realized that a mere list of equivalences was not sufficient but that definitions of terms would have to be included in the text, so that translators might have the opportunity of noting differences in usage between different languages. The Committee recommended accordingly and, the recommendation having been approved by the Union, Mr. Grebenik was requested to prepare a new text in English, making use of the basic French text. Mr. Grebenik’s new text was then revised in collaboration with M. Vincent, and a second draft produced in English and French, which was used by Sr. Ros Jimeno in preparing the Spanish version. The three drafts wrere then submitted for approval to the Dictionary Committee, the Council of the Union and a number of experts, with a view to producing a final edition.

In publishing the English, French and Spanish sections of the Multilingual Demographic Dictionary it is necessary to emphasize certain points. Firstly, the dictionary is the result of collaboration, not only between the three principal editors, but also on the part of all members of the Committee. The final version owes much to the recommendations made by a number of demographers who read various versions of the draft and commented on them, frequently in great detail. Most of their comments were accepted either in whole or in part. Some other comments the editors—perhaps mistakenly—felt unable to accept.

The editors were frequently faced with difficult problems of choice between a number of possible formulations. The nature of the dictionary, however, makes it impossible to give a detailed justification for using one version, rather than another. Final responsibility for choice rests on each of the principal editors, in this English section, Mr. Eugene Grebenik. At the same time the editors were not free to prepare a text entirely according to their own wishes. The necessity to produce parallel texts in different languages and the desire to take into consideration the comments that were made, have frequently led them to include certain expressions or definitions which they would have preferred to formulate differently had they been entirely free agents. Nevertheless, they agreed to accept responsibility for the text as it stands.

It must also be stressed that this dictionary does not pretend to be a treatise on demography. In preparing the text the fundamental aim has always been that it should serve as an aid to technical translation, and it was therefore necessary to consider the terminology of various languages in order to make the dictionary truly multilingual. Languages differ in their structure, and demographic terminology depends, moreover, not only on the language but on the development of demographic research in various countries, so that it is sometimes illogical and at variance with the requirements of science. Occasionally, terms in different languages are not wholly equivalent. In one language there may exist a profusion of terms referring to a particular subject which in another is practically neglected. In the text, notes to the different paragraphs have been used in an attempt to reduce as far as possible the inconveniences arising from these difficulties. Had the aim been to produce a set of definitions in one language, without taking account of the others, the result would have been very different. This preoccupation also accounts for a certain imbalance in the contents. It has seemed useful in certain cases to include in the dictionary terms which are not properly demographic but are frequently encountered in demographic literature and do not always appear in general dictionaries, thus causing difficulties to translators who are not expert in the subject. In considering the needs of translators the Committee has been led to adopt the principle that no opinions should be expressed on particular usages, and no recommendations made unless there was a general consensus of opinion that a particular nomenclature was undesirable. The dictionary is therefore not normative. It does not lay down new definitions. Where definitions are included, their main purpose is to establish terminological equivalences and to make them more accurate. The necessity for extreme conciseness in these definitions has occasionally led to a certain lack of precision. Standardization of definitions requires studies of a different kind. In order to avoid any misunderstanding, a list of recent documents published by various international organizations concerned with the definition of various demographic concepts is given at the end of the alphabetical index. The reader will have to consult these studies when he has to solve a problem connected with definition rather than translation.

The purpose of the dictionary will be better served if it is extended to other languages. Some sections in other languages have already been planned, or are in draft. Moreover, the Population Commission at its ninth session requested the Secretariat to study the possibility of preparing a Russian section of the dictionary. Experience will show whether the compromise that has been reached between the English and Romance languages can be extended to other Germanic and Slavonic languages as well as to those outside the Indo-European group.

Preface of the second edition (1982)

The Population Commission of the United Nations in its fourth session requested the UN Secretariat to include the preparation of a multilingual demographic dictionary in its work programme. The Union offered to collaborate in this project, and at the end of the fifth session of the Population Commission an ad hoc Committee* was given the task of drafting a multilingual demographic dictionary in English, French and Spanish.

Notwithstanding its great complexity, this work was successfully completed and the French and English volumes were published in 1958. Other versions appeared later: Spanish (1959), Italian (1959), German (1960), Finnish (1964), Russian (1964), Czech (1965), Polish (1966), Swedish (1969), Portuguese (1969), Arabic (1970) and Serbo-Croatian (1971).

At its fifteenth session, held in Geneva in November 1969, the Population Commission of the United Nations adopted a recommendation suggesting that the U.N. Secretary-General should collaborate closely with the Union in carrying out projects of mutual interest, such as the preparation of a multilingual dictionary of demographic terms.

At a previous meeting in Liege in April 1969, the Council of the Union noted with great satisfaction that the dictionary had, in every respect, come up to the expectations of demographers all over the world; the Council felt, however, that the time had come to bring the dictionary up to date, in view of the profound changes which had affected the science of demography during the decade following its publication.

A new Committee** was therefore set up, and thanks to the generous financial aid granted by the U.S. Bureau of the Census, work on the project was started in 1972 and completed in 1974.

The Committee’s field of action was not limited to its members, since a hundred or so demographic centres responded to its appeal by giving their comments on the drafts submitted to them, In this way, an immense documentation was collected which dealt not only with the definitions of demographic terms and concepts, but also with the arrangement of the book. All this was placed at the disposal of Professor Louis Henry, to whom in 1976 the Union entrusted the task of editing the final version of the second French edition of the demographic multilingual dictionary. Thus the new text prepared by Louis Henry is a synthesis of the one edited by the late regretted Paul Vincent for the first edition of the French version, and the texts prepared by the Committee on International Demographic Terminology.

The Union subsequently requested Professor Etienne van de Walle to adapt and translate the French version of the dictionary into English. I would like to take this opportunity of thanking him warmly for having successfully carried out such a very exacting task.

I also wish to expess my deep gratitude to my predecessor, Professor Massimo Livi Bacci who, during his mandate, was one of the principal promoters of this new series of dictionaries.

This English edition, following on the French one, is thus the second in a collection which will continue to increase as time goes on and provide support to the international community of demographers.

Georges Tapinos Secretary-General

* Multilingual Demographic Dictionary Committee : Chairman : P. Vincent (France), Members: C.E. Dieulefait (Argentina), H.F. Dorn (U.S.A.), E.Grebenik (Great Britain), P. Luzzato-Fegiz (Italy), M. Pascua (Switzerland), J. Ros Jimeno(Spain).

** Committee on International Demographic Terminology: Chairman: P. Paillat (France); Members: A. Boyarski (U.S,S.R.), E. Grebenik (Great Britain), K. Mayer (Switzerland), J. Nadal (Spain), S. Kono (United Nations-Japan); Observers: S. Baum and J. Siegel (U.S. Bureau of the Census — U.S.A.); Research Assistants: A. Hill (Great Britain), A. Lifshitz (France) and A. Saez (Spain).


Although many persons have contributed to various stages of the preparation of this dictionary, Etienne van de Walle would like to acknowledge the assistance of Alex Mogielnicki in translating the French version, and the advice of his colleagues, Ann R.Miller, Samuel H. Preston, Norman Ryder and Christopher Tietze who were kind enough to comment on initial versions of the English text. It owes of course a great deal to the First Edition, and to the preliminary texts prepared by the committee of the Union.

Preface of the unified second edition

The unification of the second edition of the dictionary seemed necessary when computerization of all scanned paper volumes has been performed. The Demopædia databases showed significant omissions from each of the major releases published during the 1980s (French 1981, English 1982, Spanish in 1985 and Germany in 1987). In 1988, the Arabic edition and the tri-lingual English-French-Arabic edition, had already but partially filled the gaps by comparing the French and English translations, but had failed to translate 92 new concepts introduced in the German edition. The Chinese editions (1994), Japanese (1994), Czech (2005) derived from the English version only like the Web only editions in Russian (2008), Portuguese (2008) and Polish (2010). On the other hand, the Italian edition, published on Web in 2010, drifted mainly from the French edition. Let us describe by the following example, the consequences of untranslated terms and the importance of a unified edition: a French term like “Nourrisson” which was retained, by the Commission of United Nations terminology in the 50s, and which appeared in any language of the first editions of the multilingual dictionary disappeared in the second English edition.

As an example, the forthcoming unified dictionary will be enriched by the term: nourrisson in French, lactante in Spanish, Brustkind in German, kojenec in Czech, lattante in Italian etc. or, if a common noun doesn’t exist like in English, an expression like child at the breast was used in the first English edition of 1958 and is reinserted in the unified English edition, permitting to new modules, derived from English only, to keep this lovely word, even if babies were not so appreciated before the demographic transition!

New translations into several Asian languages being under consideration due to the demographical importance of this continent, it became mandatory to achieve this unification before engaging new translations. It is still an ongoing process, concerning all languages previously published; and the first unified French language edition was published at the 46th Annual Conference of the Italian Statistical Society in June 2012 in Rome. The French edition fills a gap because the last copies of the second edition of 1981 were distributed at the symbolic price of € 1 at the IUSSP conference in Tours (2005). An Italian edition was also very necessary because the first edition was published in 1959 and had never been updated.

Harmonized editions should be available soon or later in the twelve languages already published on paper volumes and on-line in their original edition as well as in four to six new Asian languages.

Although it is regrettable that this harmonized edition is not a new edition, which could be enriched with new concepts of contemporary demography, such as reproductive health, disability and dependency, international migrations, demographic windows, decreasing population, retirement etc... But the comparisons of the first two editions demonstrated to us that the important concepts of the population sciences resided mainly in the first edition: terminological elements have been selected carefully by the Commission on Terminology of the United Nations during the ’50s in order to define our discipline and are mostly still valid.

We may also regret not having removed obsolete or even inappropriate words. Etienne van de Walle, lead author of the second English edition of 1982, told me at the Conference of Tours in 2005, that is to say, shortly before his premature death, his desire to participate in the new edition especially at removing terms on eugenics, a term or theory which already in 1981 had only an historical interest. Changes to the original editions have been done a minima, preserving the original spirit of the 1980s.

These changes justify the paper publication of this unified edition. New volume will also be available on paper once the unification in the specific language is complete. This unification is a mandatory prerequisite for a third edition.

Publishing digital books allow indeed a paper publication at low cost even if at demand. Thus the work of Joseph Larmarange, a demographer at the French “Research and Development Institute” (IRD) working at the mixed research unit CEPED, permits to download from the multilingual demographic dictionary website ( any unified edition in various electronic formats (HTML, PDF or EPUB). It is also possible to order a hard copy from a publishing company on demand. The web site is also a place for generating a “current” version of the dictionary or even multilingual indexes.

If a publication with broad distribution does not seem justified for languages that have already been published in the past, an impression "on demand" seems to meet certain needs, especially when it will be available in several languages in the same format. In addition, a print "on demand" includes the corrections of the inevitable errors and shells.

It seems to us that the main authorship of the multilingual dictionary returns to the first work of the Population Commission of the United Nations chaired by Paul Vincent. Himself is partly in debt of the revolutionary indexing system of numbered paragraph which appeared in the work of John Edwin Holmstrom. He proved in his "Report on Interlingual Scientific and Technical Dictionaries" written in 1949 that unique entries in a dictionary were inadequate when the dictionary included more than two or three languages.

Therefore, authorships are multiple and multilingual too; the detailed names are mentioned in each of the prefaces of the two possible editions which we reproduced before this current generic preface of all unified versions. If we had to mention explicit authors we should gratify, Paul Vincent for the first French edition of 1958, Eugene Grebenik for the first English edition of 1958, Louis Henry for the second French edition of 1981, Etienne van de Walle for the second English edition of 1982 and Guillermo A. Macció for the second Spanish edition. The second German edition was coordinated by Charlotte Höhn in 1987.

This multiple paternity has led us to move the status of all the different editions of the multilingual demographic Dictionary under the Creative Commons Share Alike license (CCSA). Thus, since the computerization of old paper editions, any additional work to the dictionary which is published on-line requires the acceptance of this license. It permits to consider the exact contribution of each author involved. Note also that the MediaWiki software which is used by Demopaedia for both, browsing the dictionary and editing, is also under the same open-source license.

Once we know a little handling of Demopaedia which is identical to Wikipedia, you can easily compare the text of the first edition with that of the unified edition. The digitized text uses the same paragraph numbering (101, 102 etc..), each being bundled within the same page (eg page 10 http://ko-ii.wikipedia/wiki/10). If the reader wants to know the reasons that led a writer to adopt a particular reformulation, the discussion page lists the problems that have arisen and the decisions that have been taken (eg http://ko-ii.wikipedia/wiki/Talk:10). All members of professional associations of population studies in partnership with the Demopædia project are allowed and encouraged to contribute to the discussion pages. This is already the case for members of the IUSSP and soon for members of the Population Association of America. Rights to edit the dictionary itself, that is, not only the related discussion page, are given to a limited number of authors.

It is also the goal of the project Demopædia to invite professional demographers to update the multilingual demographic Dictionary by providing this wiki platform. But as it is a first step to create new pages and even new chapters such as "reproductive health" already mentioned, we believe that it is easier to adopt a more open structure similar to that of Wikipedia, where consistency between languages is not essential. The site of this free encyclopedia is the URL for French and for the English version as well as for Korean, etc.

The new pages created gradually should allow us to better measure both, the extent of our discipline and its new terminology. A third edition of the multilingual dictionary could come someday.

The goal of science is to share results with colleagues around the world but also to fellow countrymen and thus, it seems necessary that the scientific vocabulary can be well translated and understood so that the media as well as students can use it safely. We also note that in some countries such as Sweden, there is no second edition of the dictionary, giving the impression that the scientific vocabulary doesn’t need to be renewed in Swedish, but English only. By contrast, a clear need has been felt at the IUSSP Conference in Marrakesh by Asian academics who, under pressure from many local students who do practice English, are struggling with rough translation of English demographical terms (even old terms) to be adopted by the entire community. Today, in India, there are several languages spoken by a number of users exceeding 70 million which is the total number of humans whose mother tongue is French. Malayalam is spoken, in Kerala at least, by as many speakers as Thai-speaking Thais. Hopefully this wiki platform is a multilingual opportunity to discuss the understanding of new concepts conveyed in the English scientific journals but also in international conferences still in French or Spanish and national conferences in many different languages.

This project could not have been completed without the ongoing support of the Population Division of the United Nations in the person of Hania Zlotnik who was her director from 2005 to 2012. This support took the form of the organization of Demopædia workshops, including Paris (2007) and Marrakesh (2009). Special thanks to Sergey Ivanov (UNPD), co-organizer of two workshops and author of the first draft of the Russian edition. Giudici Cristina and Elena Ambrosetti, authors of this Italian translation which has been published concurrently, have established a partnership between the University La Sapienza and the French Committee of the IUSSP, to organize a workshop on the Wiki technology in Rome in 2011. Some materials due to Laurent Toulemon’s tutorial at INED in Paris having been reused, we are extremely happy with the Franco-Italian collaboration which is driving the development of the Demopædia project, particularly in Chiang Mai at the end of August 2012. The last Chiang Mai workshop, funded by INED, co-organized by Géraldine Duthé (INED) and locally organized by Sophie Le Coeur (IRD/INED), Joseph Larmarange and Elena Ambrosetti was an opportunity to train 13 senior demographers in the Demopaedia/Wiki technology in order to produce a unified edition in six Asian new languages ​​(Korean, Indonesian, Malaysian, Nepalese, Thai and Vietnamese). They should be completed by the next IUSSP conference of Busan in August 2013.

Also thank to Christine Gandrille, secretary of the French National Committee of the IUSSP, who scanned and corrected many of the issues due to her exceptional knowledge of several languages, Françoise Gubry and Martine Deville, librarians respectively at CEPED and INED for their obstinacy to find the old dictionaries such as the Arabic or Estonian editions. Their advices in thesaurus and index technology were also very helpful.

Finally, I would like to thank the French National Committee that I had the honor to preside until January 2012 and all members of the three successive bureaus for their help in starting and conducting the Demopædia project since 2005. Websites are requesting light but continuous supports which are provided by INED in hosting the server. In 20012, IUSSP created a group of interest so that the Demopædia project could take an international dimension.

Nicolas Brouard

Director of research at INED

Coordinator of the IUSSP Demopædia project

July 2013


Notes on the use of the dictionary

The dictionary consists of a text supplemented by notes in small type and an alphabetical index. All terms which are printed in bold face in the text and the notes are listed in the index. Where an expression consisting of several words is printed in bold face it will appear in the index under each of the principal constituent words, e. g., "density of population" is indexed under D as "Density population", and under P as "Population density".

Each term has a reference number which is composed of the number of the paragraph in which it appears and an identification number. For terms appearing in the body of the text the identification number is printed immediately after the term, and for those in the notes it is the number of the note; the latter also relates the note to the corresponding term in the text. Terms occurring in the notes which are not in the text are followed by an asterisk (*) in the index and reference numbers.

Due to the harmonization of all second editions of the dictionary, new terms have been introduced in this unified second edition of the English volume compared with the original second edition of 1982. These new terms are starred (★).

Text terms with the same reference numbers in the various sections of the dictionary correspond to one another. For instance, the translator who wishes to find the equivalent French term for a given expression in English should look up the English expression in the alphabetical index of the English section and find the correspondingly numbered paragraph in the French section. It is strongly recommended that the whole paragraph in which the expression occurs in both sections should be read in order to guard against faulty translation due to slight differences in usage; this will also be useful if, in one of the languages, no term exists to express a particular concept.

Only terms in the text itself are comparable from one volume to one other using their number. Terms in the notes are specific to each volume and don’t correspond between volumes.

Different terms which are used to express the same concept have the same reference number. Any term which is susceptible of different interpretations may have two or more reference numbers which refer to the appropriate contexts.

Terms printed in bold face in notes do not necessarily correspond to one another in the different sections. Moreover, in paragraphs 303 and 344, which deal with the administrative structures of different countries and with their educational systems, there is no correspondence between the different language sections. Terms introduced in these paragraphs have no identification numbers; the paragraphs themselves are subdivided into lettered sections, A and B in the English section referring to Great Britain and the United States of America respectively.

Exploring the dictionary on

Comparing the dictionary between several languages will be easier online on the web site where hypertext links allow you to switch between the different volumes of the dictionary.

The dictionary is divided into sections or sub-chapters, each of them having is own page on the wiki. Each section is identified by a two-figures number. Usually, the section number of a paragraph corresponds to the two first figures of the paragraph number (the paragraph 104 is therefore located in the section 10). There are few exceptions: paragraphs 360, 361 and 362 are in section 35, paragraph 640 in section 63 and paragraphs 810 and 811 in section 80. Section breaks are indicated in the text by an asterism (⁂).

The URL of a section is obtained by adding the section number to Therefore, paragraph 357 could be seen online at For more details, please read online

Tools to search a term in all indexes or to generate a multilingual index are available at


Since the dictionary has been digitized, it is now available in different formats (online, printed books, electronic books...). Although this unified second edition will not change significantly, some minor corrections could be apply to the text. Therefore, the copy you are currently reading, generated at a specific date, could differ slightly from the online version.

To cite the multilingual demographic dictionary, it is recommended to consult first the last version online, the website being the reference. You can cite the dictionary as follow:

Demopædia, Multilingual Demographic Dictionary, unified second edition, English volume,, consulted the consultation_date.

If you need to cite a specific paragraph of the dictionary, indicate the number of the paragraph (as any page number will differ between the different formats). For example, to cite paragraph 211:

Demopædia, Multilingual Demographic Dictionary, unified second edition, English volume, § 211,, consulted the 21st of August 2013.

List of abbreviations

adj. adjective
n. noun
pl. plural
syn. synonym
v. verb.

Chapter 1 • General concepts


Demography1 is the scientific study of human populations primarily with respect to their size, their structure2 and their development; it takes into account the quantitative aspects of their general characteristics. It is the core of the population sciences8★, which in the broadest sense include interdisciplinary fields such as economic demography (104-1), social demography (104-2), population genetics (104-4), historical demography (102-1), mathematical demography (102-6) as well as contributions from the law, medicine, epidemiology (423-6), sociology, psychology, geography and philosophy. In statistical terminology any collection of distinct elements may be called a population3, a word that is synonymous with universe3. However, in demographic usage, the term population4 refers to all of the inhabitants5 of a given area, though on occasion it may be used for part of the inhabitants only [e.g., the school-age population (cf. 346-7), the marriageable population (cf. 514-2)]. Such groups are properly called sub-populations6. The term population is often used to denote more specifically the size7, i.e., the total number7 of the aggregate referred to in no. 101-4.
  1. Demography, n. - demographic, adj. - demographer, n.: a specialist in demography.
  2. Population, n. - Note that this term may also be used adjectivally as a synonym for demographic, e.g., in population problems, population analysis, population studies.
  3. Inhabitant, n. - inhabit, v.: to occupy as a place of settled residence.


Certain sub-disciplines within demography have received special names reflecting their objectives or their methodology. Historical demography1 deals with populations of the past for which written records are available. In the absence of such sources, the study of ancient populations takes the name of paleo-demography2 . In descriptive demography3 the numbers, geographical distribution, structure and change of human populations are described by means of population statistics4 or demographic statistics4 . The treatment of quantitative relations among demographic phenomena in abstraction from their association with other phenomena, is called theoretical demography5 or pure demography5 ; because of its resort to various mathematical methods, in practice it is identified with mathematical demography6. A piece of research that applies the tools of demographic analysis (103-1) to an actual population is often called a demographic study7. This study can focus on the current demographic situation8★ or current demographic conditions8★, i.e. the population change and its indicators during a short and recent period. All the preceding disciplines place a great emphasis on the numerical aspects of the phenomena, and are sometimes referred to as formal demography9, when they apply only to the size and structure of the population. In contrast the broader term population studies10 also includes the treatment of relations between demographic events and social, economic or other phenomena.


Demographic analysis1 is that branch of formal demography which controls for the effect of population size and structure on demographic phenomena2 by isolating the effects of each demographic variable from the others, the latter of which are called disturbing phenomena3★. It also studies the relations between demographic variables and how they interact to form population structures. A distinction is made between cohort analysis4 or generational analysis4 which focuses on a well defined cohort (cf. 117-2) followed through time, and cross-sectional analysis5 or period analysis5 which focuses on the demographic phenomena that occur during a precise time interval (such as a calendar year) among several cohorts.
  1. Cohort analysis is a form of longitudinal analysis which deals with aggregates of persons possessing the same characteristic. Panel analysis follows the same individuals case by case.


The study of relations between demographic phenomena on one hand and economic and social phenomena on the other forms another branch of the subject. The terms economic demography1 and social demography2 have been used by some writers. Demography also deals with the study of population quality3. This phrase may be used with reference to all sorts of social and personal characteristics. In a slightly different sense the term primarily refers to the distribution and transmission of hereditary characteristics (910-3) which are the subject of population genetics4 . Human ecology5 is the study of the distribution and organization of communities with attention to the operation of competitive and cooperative processes and has part of its subject matter in common with demography. Fields of research and methodology are even more intertwined in the case of demography and human geography7★. It is also the case for biometry6 or biometrics6 and epidemiology8★ which deal with the application of statistical methods to all forms of biological and medical research.
  1. Population genetics is distinct from human genetics, which deals with the transmission of inheritable characteristics in man: population genetics includes the study of the distribution and transmission of hereditary traits in plant, animal and human populations.
  2. Ecology, n. - ecological, adj. - ecologist, n.: a specialist in ecology.
  3. Biometry, n. - biometrics, n. - biometric, adj. - biometrician, n.: a specialist in biometry. The terms biostatistics, n. - biostatistical, adj. - and biostatistician, n. are frequently encountered and are synonymous with the terms given for biometry.


Finally, there is the study of population theories1. This term should not be confused with theoretical demography (102-5). Population theories are designed to explain or predict the interaction between changes in population and economic, social, psychological or other factors; they include purely conceptual treatments. Population theories occasionally form the basis of population policy2 (cf. §930), which deals with measures designed to influence population changes.


A fundamental statistical unit1 used in demography is the individual2 or person2 . The term head2 has also been employed but this usage is now largely out of date. The household3, a socio-economic unit, consists of individuals who live together. Statistical definitions of the household vary. According to the definition which has been recommended as an international standard a household consists of a group of individuals who share living quarters (120-1) and their principal meals. The term hearth3 has been used in the past, showing that in the past members of the household used to share the same fire. Classifications of households also vary between different countries and different enquiries. Most classifications involve the distinction of two types: private households4 and collective households5 . An individual living by himself is considered to be a one-person household6 . A boarder7 is a person other than a domestic servant, who is unrelated to other members of the household and who habitually takes his meals with the household. A lodger8 or roomer8, on the other hand, does not habitually take his meals with the household. These two categories may or may not be included in the household for statistical purposes.
  1. Private households are called family households when their members are related.
  2. Collective households may include institutional households composed of persons who reside in specifically designated institutions (e.g. hospitals, prisons, etc.). They may also include unrelated persons who reside in group quarters (120-1*) other than institutions. However, recent internationally recommended definitions restrict the terms household and household population to private households, and refer otherwise to persons not living in households.


When a private household (110-4) contains several persons they are called members of the household1 and one of them will be the head of the household2. There is no universally accepted rule as to who is considered the head of the household; in some cases it may be the principal earner3. On most census schedules there appears a question dealing with the relationship4 (114-3*) of members of the household to its head. This enables a distinction to be made between different groups in composite households5 or complex households5 which contain members of more than one biological family or nuclear family (113-1). A composite or complex household can be disaggregated into several nuclei6, including a primary nucleus7 and secondary nuclei8. The nuclei are more commonly called families (112-1). The primary family9★ is that of the household head when it is defined, the others are called secondary families10★. Household size11 denotes the number of persons included in the household.
  1. The term householder is sometimes used to refer to the head of the household. The term headship is frequently encountered, as in headship ratio, the ratio of the number of heads of households by age, sex or other characteristics to the corresponding categories of population.
  2. The nucleus is also called a conjugal family unit.


The family1 (cf. § 113 and § 115) is a different unit which must be carefully distinguished from the household (110-3). It is defined primarily by reference to relationships which pertain to or arise from marriage, reproduction or adoption, all of which are regulated by law or custom. The fundamental relationships are those established between a couple by marriage — and that existing between a couple as parents2, i.e., father3 and mother4, and their children5, i.e., sons6 and daughters7 .
  1. Parent, n. - parental, adj. - parenthood, n.: the state of being or becoming a parent.
  2. Father, n. - paternal, adj.
  3. Mother, n. - maternal, adj.
  4. Son, n. - filial, adj.
  5. Daughter, n. - filial, adj.


Parents and their children are sometimes referred to as the biological family1, or nuclear family1 . Brothers2 and sisters3, without distinction of sex are called sibs4 or siblings4 . Siblings with only one parent in common are called half-brothers5 or half-sisters6. Extended families7 are larger family units generally composed of combinations of nuclear families. The vertically extended family8★ consists of three or more generations living in the same household or very close to each other. The horizontally extended family9★ involves siblings with their spouses and their children living together. The vertically extended family can generate special types such as the stem family10★ in which only the heir and his family may continue to reside with their parents.
  1. The term simple family and elementary family are frequent synonyms for the terms biological or nuclear family. In a restricted sense, such as in fertility analyses, the term biological family may refer to parents and their own children, excluding adopted children.
  2. The terms composite family and joint family are frequent synonyms for the term extended family. In the most general sense of the term, an extended family may refer to all members of a kinship group.


Persons related through common descent1 from the same progenitor2 or ancestor2 are called blood relatives3 or genetic relatives3 . The terms kin3 and in an aggregate sense kinship group3 are also used. The degree of relationship4 is generally computed by reference to the number of steps which are necessary before a common ancestor is reached, but there are many different methods of computation. The fundamental relation in each of these steps is the filial relation5 (cf. 112-6* and 112-7*) of child to parent, which is the reciprocal of parenthood6 (112-2*) i.e. the relation of a couple or of a father or a mother to offspring7 or progeny7 . Blood relationship must be distinguished from relationship by marriage8, which marriage establishes between one spouse and the kin of the other..
  1. Descent, n. - descendant, n.: one linked through descent
  2. Ancestor, n. - ancestral, adj.
  3. Relative, n. - related, adj. - relationship, n.: the state of being related. The term relative is used for persons related by blood or marriage.
    Kin, n. and adj. - kinship, n.: the state of being kin. Relatives is sometimes also used for the collection of all kin.
  4. Progeny, n.: this term may also be used for all of the descendants of a common ancestor.
  5. In certain countries persons related by marriage may be referred to as in-laws.


The family1 (cf. 112-1) as a unit in demographic studies representing all or part of a household (110-3) needs to be specifically defined, and definitions for different purposes may vary. A statistical family1 or census family1 generally consists of all members of a household who are related through blood, adoption or marriage. A household may, or may not include a family. A statistical family cannot comprise more than one household, although a household may include more than one family. In some countries the definition of a statistical family may approximate to the biological family (113-1); in others the definition may be based on the family nucleus2 consisting of either a married couple without children, a married couple with one or more never-married children or one parent with one or more never-married children. These may either form the census family itself or be the core of such a family. Married couples living with their children are called traditional families3★. A broken family4★ is one in which one of the parents has been lost by death, divorce or desertion.}} Families where one parent, separated or widowed, lives with her children may be also be named single parent families4★. Married couples, widowed or separated people who, at the time of the declaration, have no more children living in the household, may have special name, like in Germany, residual family (“Restfamilie”)5★. When these types of families are living within a household, they are called family household6★.
  1. In the United States of America, a sub-family is a married couple with or without children, or a parent with one or more never-married children, under 18 years of age, living as members of a household and related to but not including the head of the household and his wife. In Great Britain, the primary family unit consists of parents and their children, the parents’ sibs and ancestors.


In demographic literature, the term generation1 has been given a precise meaning and refers to a group of persons born within a specified period of time, generally taken as a calendar year. The term cohort2 denotes a group of persons who experience a certain event in a specified period of time: thus birth cohort is a synonym for generation in the sense of 116-1, a marriage cohort is a group of persons married within a defined period, etc. In demography as in genealogy the term generation3 may also be used to denote the descendants of a group of persons who are themselves a generation in the sense of 116-1. Thus the children of a group of migrants are often referred to as the second generation9★. Occasionally we also use the expression third or fourth generation. Generations can be qualified according to their current age and, for example, the young and rising generation6★, the middle-aged generation7★ or the generation in the prime of life7★ and the older generation8★ while the age limits are often vague and therefore require clarification. Cohorts of people born during historical periods related to low birth rates (respectively high) can be referred as low-birth-rate cohorts11★ (respectively high-birth-rate cohorts10★). Occasionally consideration is restricted to lines of descent through one sex only, thus a male generation4 or paternal generation4 are the sons of a generation of males, a female generation5 or maternal generation5 the daughters of a generation of females. These distinctions are normally used when the length of a generation or mean interval between successive generations is calculated. (cf. 713-1).{Note|11|Because of the depletion of births during the first World war, particularly in France, the French term "
  1. Cohort, n.: the term cohort analysis is used to denote a method of analyzing data, in which the experience of individual cohorts is studied throughout their lives, or other specified periods.
    For purposes of military service the number of men who become liable to conscription in a given year is sometimes called the class of that year. In the United States the same term is used for a group of students who complete their studies at a particular school or university in a particular year.


A dwelling1, a dwelling unit1, or living quarters1 are statistical abstractions denoting housing accommodations appropriate for occupation by one household (110-3). The size of a dwelling is measured by the number of its rooms2 or by its surface area3. The degree of crowding4 is a function of the size of the dwelling and the number of its inhabitants. Crowding standards are applied to distinguish overcrowded dwellings5 and insufficiently occupied dwellings6 . An unoccupied dwelling7 is a dwelling which is not used for residence either permanently or occasionally.
  1. A dwelling may consist of a private house, or part thereof, or a flat or an apartment which forms part of a block of flats or tenement house. In the United States of America a distinction is made between a one-household structure and a multiple-household structure, and all persons who are not members of households are regarded as living in group quarters. Statistics of houses by the number of floors or stories are sometimes provided. It should be noted that in Europe, the ground floor is not generally counted, whereas in the United States of America it is called the first floor.
  2. There is no general rule as to whether or not the kitchen is included in the number of rooms.
  3. Overcrowded, adj. - overcrowding, n.


The occupier of a dwelling may be its owner1 or a tenant2 who rents it from an owner, who is then called landlord1. A tenant who rents a dwelling to a sub-tenant is called the principal tenant5★. A sub-tenant3 is a person who rents from a tenant. A person occupying a dwelling to which he or she has no legal title is called a squatter4 .
  1. A dwelling or apartment may be rented with or without furniture in which case it is respectively called a furnished dwelling or an unfurnished dwelling.


The terms population statistics1 or demographic statistics1 refer to numerical data2 about populations, which are based on observations3 . After such observations have been collected4 on appropriate forms (206-1), the documents are edited5 and verified5 to eliminate obvious inconsistencies. The data are tabulated6 into certain groups7 or classes8 with common characteristics. Data processing9 includes all the steps between collecting and statistical analysis10★ (132-1).
  1. Statistics, n. - statistical, adj. - statistician, n.: specialist in statistics.
  2. Collect, v. - collection, n.
  3. Edit, v. - editing, n. Verify, v. - verification, n.
  4. Tabulate, v. - tabulation, n.
  5. Process, v. - processing, n.


Data are usually referred to as raw data1 or crude data1 prior to their processing and tabulation and basic data1 or primary data1 after processing and tabulation. Basic data usually consist of series2 of absolute numbers3 which are put together in the form of statistical tables4 . In such tables the data are generally classified with respect to certain variables5 or variates5 such as age, number of children, etc., or with respect to certain attributes6 or characteristics6 (i.e. sex, marital status, etc.). Where data are classified with respect to several variables or attributes simultaneously the tables are called cross-tabulations7 or contingency tables7 . Summary tables8 give information in less detail than do individual tables9 .
  1. When the data relate to individuals (110-2) as their unit of analysis they may be referred to as micro-data. Aggregate data or macro-data relate to a unit of analysis other than an individual, for example, a nation or an administrative unit within a nation. Micro-data can be derived from several sources such as a field survey (203-5) or a sample of vital registration records. A new source of micro-data is the census public use sample, which is a systematic or a random sample of census returns that is made available for analytical purposes to interested individuals.
  2. A table which presents the distribution of a single variable or attribute within a population is generally called a frequency table.


Using the basic data generally involves two phases. Analysis1 aims at isolating the components of the observed numbers (size, structure, extraneous factors and the phenomenon under investigation); synthesis2 is the process of recombining the disaggregated components in various ways. Either phase involves the calculation3 or computation3 of indices4 which may be denoted by various names (cf. § 133). In contrast to the basic data, these indices are referred to as results6 or synthetic indices5★. In a more restricted sense an index7 (pl. indexes or indices) or index number7 is a ratio showing the value of a given quantity relative to a base8, which is usually taken as 100. Some indices are good indicators9 of a complex situation; thus the infant mortality rate is sometimes used as an indicator of the health status of a population.
  1. Analysis, n. - analytical, adj. - analyze, v.
  2. Calculate, b. - calculation, n. - calculator, n.: a machine with minimal to modest data storage capabilities designed to facilitate a modest amount of arithmetic and statistical calculating.
    Compute, v. - computation, n. - computer, n.: a machine system designed to effect the transmission, storage and calculations of large data sets; it permits arithmetic and statistical calculations as well as logical processing of data. In a dated sense, the terms calculator and computer were used to designate the person(s) engaged in the computations.


One of the first stages of analysis (132-1) consists of relating the population totals or number of events to other totals or numbers. The resulting indices are given various names. A ratio6★, also used for various purposes, is the quotient obtained by dividing quantities of the same kind. When the dividend and divisor belong to the same kind but different categories (men and women, children and women, different age-groups, for example) an other terminology might be used in non English languages, relating both quantities with a specific ratio1 (like a sex ratio). A proportion2 is a ratio which indicates the relation in magnitude of a part to the whole. A percentage3 is a proportion expressed per hundred. A rate4 is a special type of ratio used to indicate the relative frequency5 of the occurrence of a particular event within a population or a sub-population in a specified period of time, usually one year. Although this usage is recommended, the term has steadily acquired a wider meaning and is often incorrectly used as a synonym for ratio (e.g. labor force participation rate, which is actually a proportion).
  1. Proportion, n. - proportional, adj.
  2. Rates are generally given per thousand, and where the term "rate" is used without additional qualification "per thousand" is generally understood. Some rates, however, are given per ten thousand, per one hundred thousand, or per million e.g. cause-specific death rates (421-10). On other occasions rates may be given per person or per hundred. The word "rate" is sometimes omitted, thus one may find the expression "a mortality of ten per thousand," but this is not recommended.
  3. The total fertility rate (cf 639-4) is the sum of age-specific fertility rates (cf 633-9) over the age reproductive period and thus lost its inverse temporal dimension (per year). The difference is as important as between length and surface or velocity and acceleration. The term synthetic index (cf 132-5) is preferred in some languages to avoid the confusion with the inverse temporal dimension (per year) of a rate: number of demographic events divided by the time exposure or person-years. If used, the term rate in the expression ’’total fertility rate’’ refers to the implicit ’’per woman’’, which is not enough to qualify as a rate but enough for a dimensionless ratio.


The relative frequency (133-5) of a non-renewable event is often regarded as an empirical measure of the probability1 of occurrence of that event. This presumes that all the individuals who appear in the denominator have been exposed to risk3 in some way, i.e. there must have been a chance2 or risk2 that the event in question could happen to them. The use of the term "risk" does not imply that the event in question is in any way unwanted; thus the term "risk of marriage" is used. The population is often divided into different sub-groups, in which the risk of the event in question is less variable between individuals than in the population as a whole; the subgroup is more homogeneous4 with respect to the risk than the relatively heterogeneous5 whole population. Rates calculated for such subgroups are called specific rates6 as opposed to crude rates (136-8) which apply to the population as a whole. General rates7 sometimes involve an age restriction, as in the instance of general fertility rates (633-7).
  1. Probability, n. - probable, adj.
  2. Homogeneous, adj. - homogeneity, n.
  3. Heterogeneous, adj. - heterogeneity, n.


Age-specific rates1 are computed for single years of age or for age groups (age-group specific rate2★ or age group-specific rate2★). Duration-specific rates3 take into account the time elapsed since a baseline event4 or event-origin4 such as marriage or a previous birth. Central rates10 are obtained by dividing the number of events during a year, or some other period (often five years) either by the average population6 or mid-year population6 or by the number of person-years7 of exposure to the event in question during that year or period; the number of person-years is the sum, expressed in years, of the exposure time for all individuals in the observed group, over the year or period. The term rate is often used also for another type of measure, obtained by dividing the number of non-renewable events in a year or a period of years by the size of the cohort considered at the beginning of the year or period; this peasure is sometimes called an attrition probability5 or more simply a probability5, and contrasted with the central rate, defined earlier. In this paragraph, the word "period" has referred to a length of time. In the expression period rates8, however, the word is used in its chronological meaning and refers to a specific calendar year or group of years; it is opposed to cohort rate9 or generation rate9.
  1. The word quotient, used in French for this type of rate, has sometimes been used in English.


Data are called provisional1 if they are based on incomplete or insufficiently controlled observations. They are replaced by final2 data when the observations are complete. Rates based on such data are called provisional rates3 and final rates4 respectively. Where information becomes available after figures have already been published, revised rates5 may be issued. The expression corrected rate6 usually implies that defective data or inappropriate methods have yielded results which are either misleading or of limited value for the purpose in hand and that an effort has been made to correct this, e.g., correction for underenumeration, correction for migration, correction for seasonal movement. Standardized rates7 or adjusted rates7 are designed to make it possible to compare different populations with respect to a variable, e.g. fertility or mortality, where the influence of another variable e.g. age, is held constant. The term corrected rate7 has been used by some demographers as a synonym for standardized rate. When the data do not permit direct estimation of the rates (small population, for example), the use of standard rates9★ (cf. 403-6 for example) computed from data of good quality and applied to the real population, provides an indirect estimation of the expected number of events which can be compared with the observed number of events. Unstandardized rates are called crude rates8. Although they may be used to measure actual trends, false inferences may result from their uncritical use when populations with different structures (144-4) are compared.


Demographic indices (132-7) will in most cases relate to a particular period of observation1 ; this is true in particular of most rates (cf. 133-4). An annual rate2 will relate to a period of twelve months. Where observations are collected for a number of years and then averaged, the term mean annual rate3 or average annual rate3 is often used for the result. Where rates are calculated for periods different from a year they are converted to an annual basis4 through multiplication by an appropriate factor. Instantaneous rates5 are sometimes computed; they relate to an infinitesimal period of time, cf. for instance the instantaneous death rate (431-4) or the instantaneous rate of population growth (702-5).


The primary objective of cohort analysis (103-4) is the study of the intensity1 and tempo2 or timing2 of demographic phenomena. The intensity of a phenomenon initiated by one non-renewable event (201-4) may be measured by either the ultimate frequency3 of occurrence for the given event or by its complement. The ultimate frequency reflects the proportion of persons who would have experienced the event, in the absence of extraneous influences, during the existence of the cohort (116-2). The intensity of a phenomenon initiated by a renewable event (201-5) such as births or migratory moves, can be measured by the mean number of events4 per person in the cohort, also in the absence of extraneous influences. Tempo or timing may be defined as the distribution over time within the cohort of the demographic events corresponding to the investigated phenomenon. The results of cross-sectional analysis or period analysis (103-5) are summarized by period measures5 — as opposed to cohort measures6 — which can be constructed in various fashions. A commonly used technique consists in attributing the observed rates pertaining to various ages or durations to a hypothetical cohort7 or synthetic cohort7 .
  1. This ultimate frequency or its complement has received various names according to the phenomenon studied: parity progression ratio (637-7), frequency of definitive celibacy (521-1) ... It is best not to use the word proportion as part of these names, and to reserve it for observed proportions. For instance, the frequency of definitive celibacy must be kept distinct from the proportion single at a given age, as recorded in a census.
  2. It is not unusual to give the same name to the observed mean number of events per person, and to the number that would have been observed in the absence of extraneous influences such as mortality. Distinct phrases should be used; for instance, the number of children ever born (637-2) can be distinguished from cumulative fertility (636-2).
  3. Because cross-sectional analysis and hypothetical cohorts were used before genuine cohort analysis, the names of period indices often seem to imply that they refer to a cohort. This usage may lead to apparent contradictions. For example, parity-specific birth probabilities may exceed one for certain years when many postponed births are made up.


The average1 or mean1 most frequently used in demography is the arithmetic average2 or arithmetic mean2 which consists of the sum of a series of quantities divided by their number.. Where the term average or mean is used without further qualification the arithmetic average is generally meant. The geometric mean3 or geometric average3 is sometimes used when all observed values are positive. It is the Nth root of the product of N values. A weighted average4 or weighted mean4 is obtained when different items are given varying importance by multiplying each item by a particular weighting factor5 or weight5. The median6 is the value of the element which divides a set7 of observations into two halves. The mode8 is the most common or frequent value in a set of observations.
  1. Average, n., can be used as an adjective. Mean, n., can be used as an adjective.
  2. Weight, n. - weigh, v.
  3. Median, n., can be used as an adjective.
  4. Mode, n., modal, adj.


The dispersion1, scatter1, variation1 or variability1 of a set of observations depends on the differences2 or deviations2 between its elements. Here the most common measures of dispersion3 only are mentioned. The range4 is the difference between the largest and the smallest values of a set of elements. The interquartile range5 is the difference between the first and the third quartiles (142-2) and contains half the observations in the set. The semi-interquartile range6, also called the quartile deviation6, which is half the interquartile range, is often taken as a measure of dispersion. The mean deviation7 or average deviation7 is the arithmetic mean (140-2) of the positive values of the deviations of the individual items from the average, the variance8 is the arithmetic mean of the squares of these deviations and the standard deviation9 is the square root of the variance.
  1. The common notation for the standard deviation is σ.


If a series of observations is arranged in ascending order, values which have below them a certain proportion of the observations are referred to as quantiles1 or order statistics1 . The median (140-6) has been previously mentioned. Other important order statistics are the quartiles2, the deciles3, and the percentiles4 or centiles4, which divide the observations into four, ten and a hundred equal parts respectively.


A variable is continuous1 in a given interval when it can take on an infinite number of values between any two points contained in the interval. In the opposite case it is said to be discontinuous2. Where a variable can take only certain isolated values it is called a discrete3 variable.
  1. Continuous, adj. - continuity, n.
  2. Discontinuous, adj. - discontinuity, n.


The arrangement of members of a population in various categories or classes of a specified attribute or variable produces a frequency distribution1, often called a distribution1 for short. The ratio of the number in the individual group or cell — the absolute frequency2 or class frequency2 — to the total number in all groups is called the relative frequency3 in that group. In demography the terms structure4 and composition4 are often used interchangeably to describe the distribution of characteristics such as age, sex, marital status, occupation, etc. Structure is sometimes used in a more restricted sense to describe the distribution of the population according to age and sex only.
  1. The term population distribution usually refers to its spatial distribution. However, when used with the name of the characteristic or attribute that is analyzed, the word distribution is a synonym for structure or composition. Thus one finds references to age distribution, age and sex composition, and age and sex structure.


When the movement of a demographic variable in time is considered, a demographic time series1 is obtained. It is sometimes possible to decompose a time series into a trend2 around which there are fluctuations3, variations3, or deviations3 (141-2). Where such fluctuations tend to recur after certain periods, usually several years, they are called cyclical fluctuations4 or, more generally, period fluctuations4. In demography the most common period for compiling data is a year, and the fluctuations in sub-periods of a year are called seasonal fluctuations5. The fluctuations that remain after trend, cyclical, and seasonal fluctuations have been eliminated are called irregular fluctuations6. They may be due to exceptional factors such as wartime mobilization, or sometimes they are chance fluctuations7 or random fluctuations7.
  1. In a general sense the term variation may be used to describe change in any value or set of values for a variable.
  2. Periodic, adj. - period, n. - periodicity, n. cyclical, adj. - cycle, n.
  3. Random, adj.: under the influence of chance (cf. 161-1).


It is occasionally desirable to replace a series of figures by another series that shows greater regularity. This process is known as graduation1 or smoothing1, and it generally consists of passing a smooth curve through a number of points in the time series or other series, such as the number of persons distributed by reported age. If a free-hand curve is drawn the process is called graphic graduation2. When analytical mathematical methods are used, this is called curve fitting3. A mathematical curve is fitted to the data, possibly by the method of least squares4, which minimizes the sum of the squares of the differences between the original and the graduated series. Other methods include moving averages5 or involve the use of the calculus of finite differences6. Some of these procedures may be used for interpolation7, the estimation of values of the series at points intermediate between given values, or for extrapolation8, the estimation of values outside of the range for which it was given.
  1. Graduation, n. - graduate, v. - graduated, adj. Smoothing, n. - smooth, v. - smoothed, adj.
  2. Interpolation, n. - interpolate, v. - interpolated, adj.
  3. Extrapolation, n. - extrapolate, v. - extrapolated, adj.


It is often necessary to graduate distributions to correct the tendency of people to give their replies in round numbers1. Heaping2 or digit preference2 is particularly frequent in age distributions and reflects a tendency for people to state their ages in numbers ending with 0, 5, or other preferred digits. Age heaping3 is sometimes measured with indices of age preference4. Age data must often be corrected for other forms of age misreporting5 or age reporting bias5.


The numerical values of demographic functions are generally listed in tables1, such as life tables (431-1), fertility tables (634-1), or nuptiality tables (522-1). A distinction is usually made between calendar-year tables2 or period tables2 which are based upon observations collected during a limited period of time, and cohort tables3 or generation tables3 which deal with the experience of a cohort throughout its lifetime. A multiple decrement table4 illustrates the simultaneous effects of several non-renewable events, such as the effects of first marriage and death on the single population. The most used are double decrement tables4. Forecast tables5★ provide numerical values of demographic functions, like survival functions (431-6) for example, which can be used directly for population forecast (cf. 720-2). When a population is classified in two or more categories according to age, like economic status (women in the labor force or out of the labor force, for example), marital statuses, regions etc. and when continuous flows between categories are possible over time even if the individual state can usually be measured only at discrete times (waves of a longitudinal study, queries to population registers etc.), increment-decrement methods6★ or multi-state methods6★ are more and more developed and used.


Where insufficient data exist to establish the value of a given variable accurately, attempts may be made to estimate1 this value. The process is called estimation2 and the resulting value an estimate3. Where data are practically non-existent a conjecture4 may sometimes be made to establish the variable’s order of magnitude5 .


Methods of graphic representation1 or diagrammatic representation1 may be used to illustrate an argument. The data are represented in a figure2, graph2, statistical chart3 or map3. A schematic representation of the relationships between variables is often called a diagram4, for example the Lexis Diagram (cf. 437). A graph in which one co-ordinate axis is graduated logarithmically and the other arithmetically is called a semi-logarithmic graph5, though such graphs are often inaccurately referred to as logarithmic graphs5. A true logarithmic graph6 has both axes graduated logarithmically and is sometimes referred to as a double logarithmic graph6. A frequency distribution may be represented graphically by frequency polygons7 obtained by joining points representing class frequencies with straight lines, by a histogram8, where class frequencies are represented by the area of a rectangle with the class interval as its base, by bar charts9, in which the class frequencies are proportionate to the length of a bar or by an ogive10 representing the cumulative frequency distribution.


Sampling procedures1 are used to obtain information about a population from part of the population only, instead of having to study every person (110-2). The part of the population studied is called a sample2. A population is a collection of elements3 which are the object of the investigation. A sampling unit4 may be an element or a group of elements of the population and is used for selecting samples. In demographic samples the elements are usually individuals (110-2), families (115-1), or households (110-3) and sampling units may be individuals, households, blocks of houses, municipalities or areas. The sample will consist of a number of sampling units selected in accordance with a sampling scheme5 or sampling plan5.


A sample whose elements are selected by a chance process is referred to as a random sample1 or probability sample1. If a complete list of sampling units is available, this is called a sampling frame3. In simple random sampling4 a proportion of sampling units is selected from the frame at random2. This proportion is called the sampling fraction5 or sampling ratio5. Systematic samples6 are drawn systematically7 from a frame in which the sampling units are consecutively numbered. The sample is selected by taking the nth, (n + s)th, (n + 2s)th, ..., etc. unit, where n is not larger than s and is selected at random. In cluster sampling8 population elements are not drawn individually, but in groups which are called clusters9 .
  1. Random, adj. - randomness, n. - randomize, v,


In stratified random sampling1 the population is divided into a number of strata2 which are in some sense more homogeneous (134-4) than the population as a whole with respect to the characteristics studied, and a simple random sample (161-4) is drawn in each stratum. Variable sampling fractions (161-5) may be used in the different strata. Multi-stage sampling3 is a method where the selection of the sample is carried out in several stages. A sample of primary units4 is first selected and each of these units is then regarded as a population (101-3) from which a sub-sample5 of secondary units6 is selected, and the process may be repeated. When there is no good sampling frame, a sample of areas delimited on a map may be selected: this procedure is called area sampling7.
  1. Stratify, v,: divide into strata (plural of stratum) - stratification, n.


In probability sampling (161-1), chance methods are used to obtain a representative sample1 i.e., a sample which is a faithful reflection of the population with respect to all the characteristics under investigation except for random fluctuation. In quota sampling2, on the other hand, the sample is purposely selected so as to reflect the population in certain characteristics, and each interviewer (204-2) is given a quota3 of different types of sampling units which are to be included in his sample. Within the limits of the quota the interviewer is free to select the sampling units.


A population parameter1 is a numerical value that characterizes a population. Statistical estimation2 is the name given to the procedure by which the values of such parameters are estimated from the sample. Such estimates are subject to sampling errors3 and a measure of the magnitude of the sampling error is generally given by the standard error4. Sometimes a confidence interval5 is associated with an estimate to show the limits within which the estimated quantity may be expected to lie with a pre-determined probability. A difference between two values is referred to as a significant difference6 when the probability that it is due to chance is less than a given value which is called the level of significance7. Thus a difference would be significant at the 5 percent level if the probability that it could have arisen by chance is less than 0.05. In addition to sampling errors, observation errors8 or response errors8 also affect estimates. These errors usually include interviewer biases9 which are systematic errors introduced by the interviewers when the basic data are collected.

Chapter 2 • The treatment and processing of population statistics


Current population statistics1 may be distinguished from statistics of population change2. They deal with the static aspects of the subject and give an instantaneous picture of the population at a given moment of time: the statistical units (110-1) used are generally households (110-3), individuals (110-2), etc. Statistics of population change are concerned with the continuous processes of change which affect a population, and deal largely with vital events3,such as births, marriages, deaths, and with migration (801-1). Nonrenewable events4 (e.g. deaths) may be distinguished from renewable events5 such as pregnancies, births or migratory moves; renewable events are assigned an order6 based on the number of previous events of the same nature for the same person. Statistics of population change are a principal source for the study of population processes7, sometimes called population dynamics7. Censuses (cf. 202) are the main source of information on the state of the population8 . Vital Statistics (212-1) are the primary source of data for the study of population growth9 (cf. 701). Occasionally they deal with natural increase10 only, i.e. they do not take into account movement between the population studied and other populations, but logically migration statistics (812-1) are a part of the statistics of population change. The term population movement11★ is used to refer to the geographical movement of a population.


Population censuses1 are taken to obtain information about the state of the population (201-8) at a given time. Most commonly all inhabitants of a particular country are counted simultaneously:. the census is then called a general census2 Occasionally, however, only a section of the population is counted, e.g. the inhabitants of a given area, in which case the census is called a partial census3. The term "Census", however, denotes that an attempt was made to enumerate every member of the population concerned and to achieve complete coverage4 of the population. A micro census5 is limited to a sample of the population, usually large in size, and belongs in the category of sample surveys6. Censuses or surveys are sometimes preceded by pre-tests7 or pilot surveys7. To verify the accuracy and completeness of enumeration (230-2), a post-enumeration check8★ is performed using a post-enumeration survey9.
  1. Census, n. - censal, adj. The intercensal period is the time elapsing between two successive censuses.
    Modern censuses correspond to what used to be called head counts. Population counts included any estimation procedure, however imprecise, based for example on the counting of baptisms (214-2) registered for a number of years, or of hearths (110-3) or even parishes (214-1).


An enumeration1 is any operation which is designed to yield a population total. It differs from a simple count2 in that a list3 is generally prepared. An inquiry4 or survey4 on the other hand, is generally an operation which is designed to furnish information on a special subject (e.g. the labor force) and which has limited aims. A field inquiry5 or field survey5 is an inquiry in which information is obtained by personal interview6. In postal inquiries7 or mailback surveys7 questionnaires (206-3) are sent out by post with a request to return them completed. A retrospective survey8 focuses on past demographic events; in a multiround survey9 those events that occurred since the previous survey are noted from the second round on. This type of survey should not be confused with a call back10, a term used to describe the instance where the interviewer is obliged to make several attempts to reach a respondent. In censuses, information may be obtained by either direct interview11, or by self-enumeration12. In the first method, also called canvasser method11 the enumerator (204-2) notes the information provided by or about the respondents; in the second method, also called householder method12, the questionnaire is completed by the respondents (204-1) themselves. Self-enumeration may take the form of a mail census13.
  1. Enumeration, n. - enumerate, v.
  2. Count, n. - count, v.
  3. List, n. - list, v.
  4. Survey, n. - survey, v.


Persons who answer questions in a census (202-1) or a survey (203-4) are called respondents1 or informants1. Persons who collect (130-4) the information are called interviewers2, field workers2 or enumerators2, the last term being usually reserved for persons collecting information in a census. Enumerators usually work under the control of supervisors3 or inspectors3. General censuses (202-2) are usually taken by the statistical departments4 of individual countries. in England and Wales it is the [*NoteTerm!!General Register Office*], in Scotland the [*NoteTerm!!General Registry Office*]; both are headed by a [*NoteTerm!!Registrar General*].}
  1. The term interviewee is sometimes used.
  2. In the United States of America the office responsible for the census is called the Bureau of the Census;


Censuses are usually compulsory1, i.e. respondents (204-1) are under a legal obligation to provide the required information; in this respect they are different from voluntary inquiries2 (cf. 203-4), where the problem of non-response3 may become important This is particularly the case in postal inquiries (203-7), where it is often necessary to follow-up4 the first questionnaire by a second, or sometimes by a visit. Non-respondents5 are frequently divided into those who refuse6, i.e. who are unwilling to cooperate in the inquiry, and those who could not be found by the interviewer (204-2). The latter are counted as absentees7 or no contacts7. The proportion of refusals8 in response to a given question is an useful index of the reactions of the respondents. The replacement of an unusable sample unit with another unit is referred to as substitution9. j
  1. Refuse, v. - refusal, n.
  2. Absentee, n. - absent, v. - absence, n.


The forms1 used for the collection of information have a number of different names. The term schedule2 is frequently used, especially the term census schedule2. Most of the forms are questionnaires3, particularly when they are designed for completion4 by the respondents themselves. At other times, officials obtain statements5, or particulars6 which they extract7 from documents primarily used for non-statistical purposes. The questions are usually of two basic types: closed ended questions8 in which a respondent replies by selecting one out of a limited number of responses listed on the questionnaire or open ended questions9 to which the respondent may give a spontaneous answer.


A census schedule (206-2) may be an individual schedule1 containing information relating only to a single individual, a household schedule2 containing information relating to each of the members of the household (110-3), or a collective schedule3, nominal list3 or enumerator’s schedule3 on which the enumerator (204-2) enters successively data for all the persons he enumerates. There may be special schedules for the institutional population (310-7), which are called institutional schedules4.


Census operations1 usually begin with the delimitation of census areas2 and enumeration districts3. Enumeration districts in towns and cities may consist of one or several blocks4, a block being defined as a group of buildings around which it is possible to walk without crossing a street, or which are bounded by some obstacle, such as a railway line or a river. Most of the larger cities of several countries have been subdivided into statistical areas called census tracts5 which may contain one or several enumeration districts.


Vital events1 may be defined as births, deaths, stillbirths, foetal deaths, marriages, adoptions, legitimations, recognitions, annulments, divorces and separations; in short all the events which have to do with an individual’s entrance into or departure from life together with changes in civil status2. Records of these events are generally called vital records3, or registration records3. For legal reasons vital events have, in many countries, long been the object of vital registration4 or civil registration4. Birth registration5, marriage registration7 and death registration9 use special forms as birth records6, marriage records8 and death records10; these are the most common types of registration documents. The person responsible for maintaining these registers is called the registrar11.
  1. Register, n. - register, v. - registration, n.
    Civil registration systems are the descendents of parish registers (214-1) kept by the Church. A register was originally a bound book in which one or several lines were devoted to an event Today individual records often take the form of certificates. They are separate documents for each recorded vital event.


Vital statistics1 or registration statistics1 are obtained by processing the registration record or a statistical report2 established at the time of registration. Tabulations by place of residence3 of the mother or of the decedent are often regarded as more useful for demographic purposes than tabulations by place of occurrence.
  1. In many countries, the time of registration of a birth may be markedly later than the time of occurrence.


The registers mentioned in a preceding paragraph (cf. 211-4) are distinct from the population registers1 of those countries which possess a system of continuous registration2. In these registers every member of the population or every family may be represented by a card3, and the register is maintained4 or updated4 through information which reaches it through the local registration offices and through registration of any changes of residence5 (cf. 310-6). It is usually matched6 with the census results and brought up to date at regular intervals by special checks7.
  1. A card file is a collection of cards. In general, a file is a collection of records arranged in convenient order.


Historical demography (102-1) often uses documents which precede or anticipate the development of civil registration (211-4) and nominal lists (207-3) from censuses. Parish registers1 or parochial registers1 contain information on the religious equivalents of vital events such as baptisms2, religious marriages (503-2), and burials3. For chrisoms5, privately baptized infants4★ who die at home prior to a formal church ceremony, only the burial record is available. Nominal lists contain information either on a portion of the population or more rarely on the whole population. They include the a status animarum6 which are nominal lists of all parishioners, lists of communicants7 and confirmation lists8, as well as administrative and fiscal documents such as hearth tax lists9, taxation rolls10 and military conscription lists11.


Data are extracted from parish registers with the help of several types of forms1 or slips1 . These include the baptism slip2, marriage slip3 and burial slip4. The names of the subjects of record5 (i.e. the persons being baptized, buried or getting married) are inscribed on these slips, and information is recorded about the parents and other persons such as the godfather6, the godmother7 and the witnesses8. Other anonymous statements9★, nominal rolls10★ and transcription forms11 are also used for summary extraction of the data, either with or without the names of the subjects. Family re-constitution (638-2) makes use of family reconstitution forms (638-1). When genealogies12 reconstitute the descendance of an individual or a family, they are under certain conditions a valuable source of information on the demographic characteristics of the upper classes.


The process of obtaining statistical data from documents not primarily designed for this purpose is called extraction1. In general, whatever its source, statistical information is subjected to processing2 which may be manual3, mechanical4, electronic5 or a combination of these modes. Manual processing involves no equipment more complex than the desk calculator6. Mechanical processing uses tabulating machines (224-2) or punch card (224-3) machines; electronic processing uses computers (132-2*). Regardless of the mode of processing, certain types of operations7 must be performed including editing8 of the data, tabulation (130-6*) and calculation (132-2) and table preparation9. These operations are made more or less complex depending on the mode of processing which is selected.
  1. Extraction, n. - extract, v.
  2. Processing, n. - process, v. The terms to process information, data processing, are used widely.
  3. Editing, n. - edit, v. In English, the term refers to an operation performed either on the basic document or on the machine - readable data, to correct inconsistencies or eliminate omissions. In French, edition refers to the stage of table preparation.


Editing the data usually requires the prior coding1 of a certain number of entries on the basic document2. The coding scheme3 establishes a correspondence between an entry and its translation into numeric or alphabetic codes. The code book collects and describes the coding schemes used with a particular set of basic documents. A coding scheme is usually designed to facilitate later groupings of the data. In contrast, a classification4 is a mere list of individual codes where each heading5 is given one or several numbers. After the data have been coded, they constitute a file (213-3*) which can be converted to machine readable form. The second stage in the editing consists in the cleaning6 of the file, through elimination of errors by validity checks7 and consistency checks7; these can be internal checks within each statistical unit (cf. 110-1) or may result from the comparison of different units. After errors have been identified, they may be corrected in the original document or the file by some automatic procedure.
  1. Code, n. - code, v. - coding, n.


The edited data are rarely used directly; they are subjected to grouping (130-7) and tabulation (130-6*), and this normally leads to a presentation in the form of statistical tables (131-4). These may be the outcome of sorting1, either manual or mechanical, resulting in the reorganization of the elements in a set according to predetermined rules, or more simply of a systematic count of the elements presenting a selected characteristic. The choice of elements or of characteristics may be based on the values of one or several quantitative attributes, or on the modalities2 of one or several qualitative attributes. Few studies can do without computation, simple or complex, isolated or repetitive, and the computer (225-2) now allows calculation that would have been too lengthy by hand. These capabilities have led to the development of techniques of data analysis3. Deterministic and stochastic models (cf. 730) often require considerable computations, and so do simulations (730-6).
  1. Sorting, n. - sort, v.


The stage of table preparation (220-9) aims at making the results of processing conveniently available in the form of listings1, numerical tables (131-4) or charts (155-2), all of which are commonly used in descriptive statistics2. The use of computer graphing3 and computer cartography3 permits the mass production of graphical presentation at a preliminary stage.


Purely mechanical processing (220-4) did not involve the use of electronic equipment1 which has come to replace the earlier tabulating machines2 or unit record machines2 and is much more versatile. In most instances the information is coded (221-1*) first, and then transcribed onto punch cards3 by using a keypunch4. A card verifier5 is a device used to check the accuracy of the punching. These two types of unit record machines remain in common use since the punch cards are still a frequent way of entering data into the computer. The use of other types of unit record equipment such as the card sorter6 and the tabulator7 has declined. Increasingly, the data are entered directly on magnetic tapes (cf. 226-4) or disks (cf. 226-5) without resorting to punch cards.
  1. Punch cards or punched cards.
  2. Keypunch or card punch.


Demographic research depends heavily on electronic data processing1 using the computer2. The term hardware3 refers to the physical component, whereas software4 supplies the user5 with ways to have access to the computer. Computer specialists6 include programmers7 who write programs8 conceived by system analysts9.


The hardware (225-3) components of a computer (225-2) include one or several central processing units1, a central memory2, one or more mass storage devices3 which use magnetic tapes4 or disks5 and a set of input-output devices6. The software (225-4) components include the operating system7, which has the task of efficiently managing the available facilities8 for the users (225-5) running the users’ programs9 and the processing programs10 which are preestablished programs (225-8) designed for the solution of standard problems.


A user (225-5) can process his problem by writing a program (225-8) in a general programming language1 such as Fortran, Cobol, Basic or Algol, or a specific language, designed to use the processing programs (226-9) stored in the central memory (226-2) of the computer such as a data base management system2 used to create and maintain a data bank2, a survey processing program3 or a statistical package4. The devices which are used to enter and receive information from the computer can differ according to the mode of processing. In batch processing7, the normal input and output units are the card reader5 and the line printer6. A console8 is the normal input and output unit for processing in a timesharing mode9. In either instance the entry units may be spatially separated from the computer and processing under these conditions is accomplished by remote terminal10.
  1. In addition to programming languages as defined above, other types of languages can be used to manipulate the operating system; these are usually referred to as job control language.


Any information processed in a computer (225-2) undergoes three main phases. First, data entry1 or input1 which may be done by using punched cards (224-3*) or by using an on line2 device such as a keyboard console (227-8). Data which is already stored in the computer may be accessed from either central memory (226-2) or from one of the mass storage devices (226-3) and used as input data. This is part of the data collection3★ which goes from extraction (220-1) to the transcription on an electronic medium, through validity checks (221-7) and consistency checks (221-18 that can be made ​​during data entry when working on line. The second phase, processing (220-2), is divided into two main types: numerical processing4 and non-numerical processing5. Statistical or arithmetic computations are normally the operations contained in the former while data manipulation operations are the focus in the latter. In a third phase, occasionally referred to as output phase, the processed results6 or output6 may be printed out on the line printer (227-6) or saved as a file on a mass storage device (226-3) for further processing. Results may also be diverted to a plotter7 to obtain processed results in the form of a graph or a figure.


The accuracy1 of population statistics will depend among other factors on the completeness2 of the count of individuals, groups or events on which they are based. Omissions3 and undercount3 tend to generate underestimation4 while multiple counting5 leads to over-estimation6. Additional sources of error include misreporting7 of a characteristic such as age and classification errors8. Such inaccuracies are sometimes detected by post-enumeration tests9 or quality checks10. Occasionally certain questions are not answered or insufficiently answered and this may lead to considerable inaccuracy, the incidence of which is indicated by the frequency of the class designated as non-response11, not stated11, unknown11, undeclared11, not specified11, poorly defined11 or misspecified11 etc...
  1. Accuracy, n. - accurate, adj.
  2. Completeness, n. - complete, adj. The terms "complete" and "completeness" are used here to express the absence of omissions. The same terms may also be used to refer to coverage, as in 202-4.
  3. The omission of some events from vital registration is called underregistration, and from a census or survey, underenumeration.
  4. The expression double counts is often used in this sense.

Chapter 3 • Distribution and classification of the population


Population statistics are generally presented in terms of the geographical distribution of the population1 or the spatial distribution of the population1, and also by structure (144-4). Each population lives in a given area2 or territory2 (305-6), and the study of the geographical distribution3 or spatial distribution3 deals with the way in which they are distributed over the territory.
  1. Territory, n. - territorial, adj.


The territory (301-2) in which a population lives will generally be divided into sub-areas1. For administrative purposes it may be divided into administrative areas2, administrative units2 or administrative districts2 sometimes known as legal divisions2 or political divisions2. Geographers on the other hand, may divide the area into regions3 or zones4 which may or may not correspond to administrative units. The term "region" or "zone" may be used in a number of different senses and the areas referred to may be of very different sizes. Thus one speaks of the polar regions, of climatic zones or of metropolitan regions. The terms natural region5 and economic region6 are used by geographers. The term natural area7 is used in human ecology (104-5) to define an area occupied by a population with distinct characteristics.


Administrative units differ from country to country and over time in the same country, so that the same word may cover different situations. Minor civil divisions include townships1 and parishes1; major civil divisions receive names such as states2 or provinces2, and intermediary units are often called counties5 and districts6. In Canada, for example the main administrative divisions, by increasing order of size, are the township8, the county9 and the province10. As an other example, the main administrative division in France are now the regions2 which correspond to the province and the departements 3★ which correspond to the cantons4★ in Switzerland where districts7★ and circles11★ are minor civil divisions. In the United States, parishes are equivalent to counties.
  1. Villages, boroughs and cities are other names sometimes given to the smaller administrative units. Municipality is a general descriptive term for minor civil division.


A population may be settled1, sedentary1, or nomadic2, i.e., migrating back and forth within a given area and without fixed abode. Nomads who are in the process of becoming settled are called semi-nomadic3. Occasionally primitive peoples may have a territory allocated exclusively to themselves called a native reserve4 or reservation4.
  1. Nomadic, adj.- nomad, n.


A country1 is usually the territory (301-2) of a people2 (cf. 333-3) or a nation2. Persons belonging to a nation share, in general, a common culture. A state3 is a political body. The term may be used in two different senses: most commonly a state is a body possessing full sovereignty in its territory and over its inhabitants. However, a number of federations4 of federal states4 are divided into smaller units which are also called states5 and whose sovereignty is not absolute (e.g. in the United States of America and Australia). The term territory6 (301-2) is generally used for a geographical area, but it is occasionally used to denote a political unit which has been settled relatively recently. A distinction is sometimes made between self-governing territories7 and non-self-governing territories8.
  1. Nation, n. - national, adj.


Within a territory (301-2), certain terms are used to describe different kinds of conglomerations1 or aggregations1 of population, sometimes known as population aggregates1, population clusters1 or more generally as localities1. In rural areas, the smallest unit is referred to as a hamlet2, which generally consists of a very small collection of houses. A slightly larger conglomeration is the village3 which is generally a small community and which may have a mainly agricultural population. A town4 or city4 is a larger conglomeration in which there are in general few people engaged in agriculture, but the point at which the transition from village to town or city occurs is difficult to specify and varies in different countries. The seat of government of a territory (in the sense of 305-1), is called its capital5. In a county, the place where the local government is situated is called the county town6 or county seat6. Towns and cities may be further divided into districts7 or quarters7 and for electoral purposes into wards7.
  1. The term agglomeration is also used in this sense. See however 307-1.
  2. A very large town or city is sometimes called a metropolis, n. - metropolitan, adj.
    Town, n. - urban, adj.


Continuously built-up areas may arise through the coalescence of neighboring localities which, while retaining their administrative independence, may constitute one agglomeration1, containing a central city2 and suburbs3 with specialized functions. The terms conurbation4 or metropolitan area4 are generally employed to designate a number of different agglomerations which, though geographically contiguous, have retained their own individuality. In many cases, however, the term conurbation is used as a synonym for agglomeration. The fusion of conurbations and large cities leads to the megalopolis5 or metropolitan belt5 which may extend over a large area. Metropolitan regions6★ may refer to agglomerations which include the commuter belt.
  1. Another term used as synonym is urban nucleus.
  2. Other terms used as frequent synonyms are satellite communities and suburban zone.
    Suburb, n. - suburban, adj. - suburbanization, n.: the process of rapid population growth in the suburban zones adjacent to a large city. Densely populated areas contiguous to large cities are occasionally referred to as the urban fringe, and the zone marking the transition between urban and rural settlement, as the rural-urban fringe or exurbia.
  3. Urban populations are often regrouped in statistical areas such as the standard metropolitan statistical area (United States), the densely inhabited district (Japan) or the conurbation (England).


In census practice a distinction is made between the resident population1 or de jure population1 of a given area, which consists of the people who habitually live in that area, and the actual population2, or de facto population2, which is made up of the persons in the area on census day. In the resident population, temporary absentees4 are included with those permanent residents3 who are present in the area on census day; the actual population consists of residents together with visitors5 or transients5. The two methods of enumeration will give different results even for the country as a whole. The place where a person lives is called the place of residence6. For administrative reasons, certain persons who live together in large communities (i.e. boarding schools, military persons in barracks, prisoners, etc. (cf. 110-5*) are often separately enumerated. These persons form the institutional population7. Special rules are used to enumerate vagrants8 or persons of no fixed abode8.
  1. The term domicile is a technical legal term for legal residence and denotes the place where a person is legally deemed to reside. This may differ from his actual residence. In the United States of America, the de jure population is the population of usual residence.
  2. In the United States of America the term institutional inmates is reserved for persons living under care or custody in correctional institutions, hospitals for mental disease and tuberculosis, homes for the aged, handicapped and dependent or neglected persons; other residents of group quarters include such persons as students in college dormitories, or soldiers in military barracks.


In many countries a rural area1 is defined as an administrative district in which the population size is below a certain level (often taken as 2,000). Other areas are called urban areas2. The rural population3 is the population living in rural areas, the urban population4 that living in urban areas. Criteria for allocating the population of particular areas to the rural or urban sector respectively differ in different countries. Certain definitions of rural and urban population may lead to distinguish an intermediate category referred to as the semi-urban population5.
  1. Rural, adj. - realization, n.: growth in the proportion of persons living in rural areas.
    Rural population should not be confused with agricultural population or farm population (359-2).
  2. Urban, adj. - urbanization, n.: growth in the proportion of persons living in urban areas.


The density of population1 or population density1 is an index showing the relation between a population and the area in which it lives. The simplest density index2 is obtained by dividing the total population by the area of the territory and is generally expressed as the number of persons per acre, square kilometre or square mile. The scatter of the population3 depends on the type of settlement4, grouped settlement5 or dispersed settlement6. Some writers have computed the population center7 of a given area by the methods used to find the center of gravity in applied mathematics; each individual in the population is given an equal weight.
  1. Density, n. - dense, adj.


Where the pattern of settlement of different populations is to be compared and other factors besides surface area are taken into account, comparative density indices1 are sometimes computed. There are various such indices, among which we may mention the density of population per unit of cultivable area2 and the density of the agricultural population per unit of cultivable area3. Occasionally these indices are based on the cultivated area4 rather than the cultivable area5. The density may also be expressed as a relation between population and total economic resources; the maximum potential density6 or population carrying capacity6, showing the relationship between resources and the maximum population that can be supported with these resources, may be considered. The concept of optimum density7, i.e., the density which will give the maximum real income per head with given resources, is used in population theory.


The sex structure1 or sex distribution1 of the population is measured by the ratio of the total number of one sex2 to the total number of the population or, more frequently, to the total number of the other sex. By convention, the male sex is usually considered in the numerator and we speak of the masculinity3 of the population. The masculinity proportion4 is the proportion of males in the total population. The sex ratio5 is the ratio of the number of males to the number of females; it is usually expressed as an index value (132-7) i.e. the number of males per 100 females.
  1. Occasionally, the numerator of this ratio relates to the female population, and the feminity of the population is measured.


The terms males1 and females2 are commonly used in demography in place of men1 and women2 to refer to persons of each sex at all ages including children (323-3). In a similar fashion the terms male child3 and female child4 replace boy3 and girl4. The term man is also used in the general sense of human being5★.


Age1 is another fundamental characteristic of population structure. Generally it is expressed in years, or years and months; in the case of very small children, it may be given in months and days, or in years and decimal fractions of years. Demographers usually truncate the age to the number of complete years2 lived, and this is called age at last birthday3. Occasionally demographic statistics refer to the age reached during the year4. Where the fraction of the last complete year lived is counted as a whole year, as in some actuarial applications, we speak of age at next birthday5. Stated age6 or reported age6, in a census or vital registration, is often rounded upward to the next integer especially when the next birthday is near. The term exact age7 is used, particularly in life table calculations, to denote the time when an individual reaches his birthday. Census questions include either the date of birth, age at last birthday, or even simply age without further precision. When the knowledge of ages is not widespread, a historical calendar8 may be used to estimate ages. This is a list of events with a known date that occurred during the lifetime of the respondents.
  1. Thus, age groups (325-2) are usually expressed in completed years and the group aged 6-13 years includes the individuals whose exact ages (322-7) are comprised between 6 and 14 years.


In demography, certain terms which have been taken from everyday language are used to denote different stages of life1 or an approximate range of years. At the beginning of life comes childhood2. In general a child3 is a person who has not yet attained puberty (620-2). In the very early days of life, the child is called newborn4. A child at the breast5★ is a child who has not yet been weaned from its mother. The term infant6 may be used to denote a child who has not reached its first birthday, though in colloquial language it may be applied to slightly older children. Children who have not yet reached the compulsory school age are called pre-school children7, a school-age child8 is a child at an age at which it is customary to attend school.
  1. Infant, n. - infancy, n.: the period of being an infant - infantile, adj.


Childhood is followed by adolescence1 or youth1 which starts at puberty < 620-2). The terms adolescents2 or young persons3 are employed for men and women between childhood and adult age4. Those who have reached maturity4 are called adults5. Old age6 is frequently used to define the period of life during which most persons are retired. Persons above that retirement age7★ are called old people8, the aged8 or the elderly8.
  1. The term youth is also employed collectively. When used in the singular, it more frequently refers to a male. In the United States of America, teenager refers to persons in their teens, i.e., between 13 and 19 years.
  2. Maturity, n. - mature, adj. - maturation, n.: the process of growing to maturity.


The age distribution of a population is either given by individual years of age1 or by age groups2, which may be five-year age groups3, also called quinquennial age groups3, or broad age groups4, such as 0-19 years, 20-59 years, 60 years and over. Occasionally a population’s age distribution6 or age structure6 is given by classifying the population by year of birth5. Graphically an age distribution may be represented by a population pyramid7 which is a histogram (155-8) showing the population by age and sex and so named because of its pyramidal shape.


The mean age1 of a population is the average age of all its members, the median age2 is the age which divides the population into two numerically equal groups. When the proportion of old people in a population increases, we speak of the aging3 of the population. An increase in the proportion of young people involves a rejuvenation4 of the population. An old population5 has a high proportion of old people, a young population6 has a high proportion of young people or children. The term aging used above should not be confused with the technique used in population projection, which consists of aging7 a population by applying survival probabilities (431-6) by age to determine the number of survivors at a later date.
  1. Also written ageing.
  2. The word younging is used by American demographers.


Aging (326-3) of a population must also be distinguished from individual aging1 or senescence1, and from an increase in the duration of human life or increased longevity2 which is the result of improved standards of living and of medical progress. An individual’s physiological age3 will depend on the state of his tissues and organs. In the case of children we speak of mental age4, which is defined as the age at which the attainments of the individual child as measured by certain tests can be performed by the average child. In studies of mental and physiological age, a distinction is made between these ages and chronological age measured by the time elapsed since the individual’s date of birth5. The ratio of mental to chronological age is called the intelligence quotient6 (often abbreviated to I.Q.).
  1. Senescence, n. - senescent, adj.


Inhabitants of a nation or state may be subjects1 citizens1 or nationals1 of that state, who enjoy certain political rights, or they may be aliens2 or foreigners2 who are citizens of another state, or citizens of no state at all and called stateless3. The term “subject” used to have a servile connotation but has tended to lose it and is frequently taken as a synonym of citizen, though occasionally a distinction is made between a subject and a citizen. Citizens of a state generally possess the nationality4 of that state. This term is nowadays used as a synonym for citizenship4, but in some multi-national states6 a distinction may be drawn between political nationality4 and ethnic nationality5.


Aliens may acquire the nationality of their country of residence by naturalization1 and become naturalized citizens2 of naturalized persons2. In some countries certificates of naturalization3 may be revoked4 and naturalized persons will then suffer loss of nationality5. Persons may occasionally have more than one nationality, and will then be said to possess dual nationality6. A distinction is sometimes drawn between resident aliens7, who habitually live in a country other than their own, and alien visitors8 or visiting aliens8, who are there only for relatively short periods.


Individuals born in the territory in which they live are called natives1 of that territory. If their ancestors were among the original inhabitants of that territory, they are called autochthonous2, indigenous2 or aboriginal2 inhabitants; the last term is often reserved for primitive peoples. Statistics frequently distinguish between native-3 and foreign-born4 individuals.
  1. Aboriginal, adj. - aborigines, n., pl.


The term race1 is generally taken to mean a group of persons with certain common physical characteristics which are hereditarily transmitted. In some census practice, the term is sometimes used more loosely, sometimes for a group of people bound together by a common culture or national origin, or even for people inhabiting a given territory. Another term which is sometimes used is ethnic group2 and here again there is no uniformity in meaning. Ethnic group generally refers to a group of people with common culture, language, or religious traditions. An ethnic group may be a racial group. A people3 (cf. 305-2) is generally a collection of persons who are linked by a common past or a common culture. Persons living is a given territory who exhibit notable difference from the majority of the population are called minorities4, e.g., ethnic minorities4, national minorities4, linguistic minorities4, or religious minorities4.
  1. Race, n. - racial, adj.
  2. Racism, n.: theory that certain races are inherently superior to others; racist, adj.
  3. Tribe, and tribal group, still used in certain contexts, tend to be replaced by "ethnic group".


Individuals are sometimes distinguished by their color1, which is used loosely to refer to the apparent pigmentation of the skin. In some countries a distinction is drawn between white persons2 and colored persons3 sometimes called non-whites3. Mating between persons of different colors is sometimes referred to as miscegenation4. A person who is the issue of such a union is said to be of mixed blood5 or mixed parentage5.
  1. Crossing is sometimes used in that sense. It also refers to the change in racial self-identification of an individual between one date and another.
  2. The issue of a white and a negro is called mulatto. In Spanish America the issue of a person of European extraction and an American Indian is called a mestizo. The issue of a person of European extraction and an Asian is sometimes referred to as an eurasian.


The population may be classified by the language1 or dialect2 habitually spoken. A distinction is drawn between an individual’s mother language3 or mother tongue3 which is the language spoken in his home in his earliest childhood, and his usual language4, which is the language customarily used by him. The distinction between the two is not always very easy among people who are bilingual5 or multilingual5. The statistics that present information on these topics are called statistics of language6.
  1. Language, n. - linguistic, adj.
    Linguistics, n.: the study of the nature, structure, origin and meaning of language and human speech.
  2. Dialect, n. - dialectal, adj. A dialect is a variety of language that is distinguished by its pattern of pronunciation, grammar or vocabulary.
  3. Bilingual, adj. - bilingualism, n.


Religious statistics1 divide the population by religious affiliation. A distinction is generally drawn between the major religions2 and their principal denominations3, rites4 or sects5. Persons who have no religion may describe themselves as agnostics6, freethinkers6 or atheists6.
  1. Rite, n. may also be used in the sense of a religious ceremony.


The population is also often classified by educational status1. Individuals who can read and write are called literate2; those who have reached a certain age and cannot are illiterate3. Often completion of a particular grade or level of schooling is assumed to confer literacy. Educational attainment statistics4 classify individuals by grade attainment5, years of school completed5 or, more rarely, by age at leaving school6. Another type of classification is based upon the diploma7, degree7 or certificate7 obtained, and depends on the organization of instruction8 in each country.
  1. Literate, adj. - literacy, n. Literacy statistics are the part of education statistics that refer to the ability to read and write. The literacy ratio is the proportion of the population covered that is literate. Its complement is the illiteracy ratio.
  2. Illiterate, adj. - illiteracy, n. A person who is able to read but not write may be called semi-literate, and such persons are sometimes classed with the literate and at other times with the illiterate population.
  3. The school-age population (346-7) is often classifed by grade or level of enrollment, and attainment is then presented only for the population beyond normal school age.


The education system1 includes all institutions, public and private providing instruction in a country. Where both types exist a distinction is made between public education2 and private education3. After pre-school education4, it is usual to distinguish between three levels of education5 which are in ascending order: primary education6, secondary education7, itself often divided into several cycles8 or tracks8, and higher education9. The latter includes, among others and at different levels10★, courses of study that lead to a university degree11. Technical education12 or vocational education12 may be offered either at the secondary or higher education level.


Types of educational institutions1 and their names are a function of each country’s particular educational system. Pre-school education (343-4) is offered in nursery schools2 or kindergartens2. The institutions that offer the three levels of education mentioned above (343-5) are usually called respectively: primary schools3 or elementary schools3, secondary schools4 and colleges5 or universities5; in addition to the latter, there may be various kinds of professional schools6. Technical education (343-12) is given in learning centers7★, technical schools8★, technical colleges9★, technical institutes10★ and educational institutes11★.
  1. The term college is used in a variety of senses; a university college is either an institution of higher learning which has not full university status, or it may be a constituent college of a university.


A class1 (cf. 130-8) is a group of pupils2 with the same teacher3 who meet in the same class-room4 and are generally instructed simultaneously. A group of pupils who are at the same level of educational advancement are said to be in the same grade5 in the United States of America, or in the same class5 or form5 (cf. 206-1), in Great Britain. The term student6 is generally used for those receiving higher education, but is also interchangeable with “pupil” at the secondary level.
  1. A scholar in Britain is generally a pupil or student who has been given a scholarship from public or private funds; the use of the term as a synonym for pupil is archaic. In the United States of America such a student would be called a scholarship holder or scholarship student.
  2. A university student who has not yet taken his first degree is an undergraduate. A graduate (cf. 151-1*) in Great Britain is the holder of a university degree; in the United States of America the term may be used for anyone completing his studies at the university, high school, or even primary school. In the U.S., a graduate student is one who is pursuing a second degree, the equivalent of a post-graduate student in the British system.


Current school statistics1 may distinguish between the number of pupils enrolled2 and the number of pupils in attendance3. A comparison of these two figures gives an attendance ratio4. Compulsory education5 implies the existence of a range of ages where school attendance is obligatory by law. This makes it possible to specify the number of children of school age6 or the school-age population7 according to a legal criterion.
  1. The attendance ratio is the ratio of pupils in attendance to pupils enrolled, whereas the enrollment ratio is that of pupils enrolled to the school-age population.


Other statistics concern educational progression. An individual progresses normally grade by grade, from the lowest class of elementary school, to the end of his studies. Leaving school1, where compulsory education is enforced, is exceptional during school age, barring illness or death. The dropout rate2 is the probability of leaving school before obtaining a degree, either during the year or at the end of a grade, and it is constructed in the same way as a probability of dying in a life table; its complement to one is the retention rate3. Such rates can be used to compute a table of school life4, from which it is possible to infer the mean length of education5. At the end of the school year, pupils or students who do not terminate their studies, may either repeat the grade or move on to the next grade, with or without change of track6. According to the fate of these pupils or students at the end of the academic year, proportion repeating a school year7★ are established.


A distinction is generally made between the working population1 or economically active population1 and the unoccupied population2 or economically inactive population2. Generally speaking, the working population consists of those individuals engaged in gainful activities3. A gainful activity, or economic activity3, is an activity which contributes to the production of income. Unpaid family workers (353-5) are usually included in the economically active population. Homemakers4 or housewives4 engaged in unpaid domestic duties, students, retired workers, etc. are usually excluded. The members of the economically inactive population are sometimes referred to as dependents5 (358-1) in the sense that they subsist on the product of the working population. (See, however, the different sense of this term stated in § 358). The ratio of the working population to the total population, usually computed with reference to a given sex-age group or other category, is called the activity ratio6 or labor force participation ratio6.
  1. The terms gainfully occupied population, gainful workers, labor force are used as synonyms for working population and economically active population.
    For statistical measurement of the working population, the gainful worker concept or the labor force concept may be used. According to the gainful worker concept, the working population is defined as being composed of those persons who have a gainful activity which they normally exercise. According to the labor force concept, it is defined as the group of persons who were working at a gainful occupation or wanting or seeking such work during a specified period preceding the inquiry.


Workers1 who make up the working population can be classified as employed2 or unemployed3. Under the labor force concept (350-1 *), only persons who were actively seeking work4 or are on temporary layoff during the specified period are usually counted as unemployed. It is important to distinguish between persons who have never had a job and persons who are looking for their first job11★ or first-time job seekers11★. The employed population5 consists of all those currently working for pay or profit. Among the economically active, a substantial portion of workers may be compelled by the economic conditions of the country or of the time, to perform less work than they would normally be able and willing to perform; in this instance, the terms underemployment6 or partial employment6 are used. Marginal workers7 who only very occasionally participate in economic activity, are most often classified as not in the labor force under the gainful worker concept (350-1 *). The employment to population ratio8★ is the proportion of employed persons in the working age group (usually 15 to 64). Inactive persons9★ are those who do not accomplish any kind of professional activity neither are looking for any employment. Hidden unemployment10★ or labor reserve10★ includes people who, although not officially registered as unemployed, are looking for a private work as well as those who do not exercise nor are looking for a job but if some job opportunities arose to them, could respond.
  1. Employed, n. and adj. - employment, n.: situation of an individual exercising an economic activity. Employment status refers to the classification as either employed or unemployed.
  2. Unemployed, n. and adj. - unemployment, n.
  3. One refers occasionally to underutilization of the labor force. Under-employment and underutilization also sometimes refer to the situation of persons who perform below their level of qualification.


The occupational classification1 of the working population (350-1) shows its members grouped by occupation2. The similarity of the work done by workers, including the similarity of skills and training required are the main criteria used for grouping occupations into occupational groups3 or occupational classes3.
  1. For purposes of comparability, the International Labour Office has prepared an International Standard Classification of Occupations.


The working population (350-1) is also usually classified by work status1. In this classification employers2 are distinguished from employees3 on the one hand and from workers on own account4 or independent workers4 on the other. The latter do not employ labor for pay, but they, as well as employers, may be assisted by unpaid family workers5 or family helpers5 who are usually distinguished as a separate group. A combination of occupational and status classifications may be used to construct social status categories6.
  1. The classification by status (as employer, employee, etc.) is designated by many different terms in the censuses of various countries, including “industrial status”, “states in employment”, “position in industry”, “class of worker”, etc.
  2. Managers are sometimes counted with employers though they are themselves employed.


Various sub-groups of the category of employees (353-3) are sometimes distinguished. One such sub-group is home workers1 or cottage workers1, who work in their own homes, sometimes for several employers. Among the employees a distinction is sometimes made between manual workers2 and non-manual workers3 or clerical and office workers3. Manual workers may be further sub-divided according to their skill4, with skilled workers5, semi-skilled workers6, and unskilled workers7 being distinguished. Apprentices8 are sometimes shown as a sub-category of employees.
  1. Another type of classification of employees is that which distinguishes between wage earners who are paid daily or weekly and salaried employees who are paid monthly or at even less frequent intervals. The statistics of the United States distinguish four broad occupational categories: white collar workers; blue collar workers, including craftsmen, operatives and non-farm laborers; service workers; and farm workers (cf. 356).
  2. A laborer is an unskilled worker, who does very heavy physical work.


Among the employees (353-3) a distinction is often made between the managerial staff1, who make policy decisions; the executive staff2 who apply the decisions; and supervisors3 or foremen3 who direct the operative. Officials () are divided into simple or lower service4★, mainly for positions of menial work(eg, administrative assistants, technical assistants), middle service5★, mainly for positions requiring roughly the equivalent of a completed apprenticeship (eg, editors, administrative secretaries), upper service6★, mainly for positions requiring a Bachelor’s degree or its equivalent (administrative frameworks or technical) and senior service7★, restricted to graduates holding a Master’s degree or its equivalent.
  1. The term executive in the United States of America refers to a member of the managerial staff.


Special classifications apply in agriculture. Farmers1 or farm operators1 are those who farm the land for profit; among them we distinguish between farm-owners2, who own their land, tenant farmers3, who rent it from a landlord, and share-croppers3, who give a portion of the crop in return for the use of land and livestock. Agricultural laborers4 are persons working who are employed by farmers.
  1. A farm manager who is salaried is generally classed as a farmer.
  2. In Scotland a small farmer is sometimes called a crofter. A farmer with a very small farm is also known as a smallholder.
  3. Agricultural laborers are of three general types: fulltime agricultural laborers, day agricultural laborers, and seasonal agricultural laborers. This last category often consists of migrant laborers.


The working population may also be classified by industry1 or branch of economic activity1. This classification depends on the nature of the firm2 or establishment2 that the individual works for. Generally importance is attached to the division of the population into agricultural workers3 and non-agricultural workers4. Government employees5 are sometimes, and military personnel6 or members of the armed forces6 are generally shown separately, but employees of public enterprises are counted as a rule with the rest of the industrial population. Industries are generally classified in three sectors, the primary sector7 (agriculture, hunting, fishing and mining), the secondary sector8 (manufacturing, construction and utilities), and the tertiary sector9 (commerce, finance, transport industries, and service industries). In developing countries the traditional sector10 is often listed separately and opposed to the modern sector of the economy.
  1. For purposes of international comparability, the United Nations have prepared an International Standard Industrial Classification of All Economic Activities.
  2. A civil servant is an employee (353-3) of the central government. An official is an employee of a public body but the term is occasionally used for salaried employees of large companies. A distinction is often drawn between government employees and private workers.


The economically inactive population may be divided into dependents1 (350-5) and self-supporting persons2. Dependents depend for their support on the efforts of earners3 or breadwinners3; this is for example the case of housewives (350-4) and dependent children4. Self-supporting persons have sufficient means for their subsistence. They may be rentiers5 or persons of independent means5, retired persons6 or pensioners6. A special category of dependents is that of persons receiving public assistance7 or public welfare recipients7. Persons incapable of work are called unemployable8. The ratio of the inactive to the active population is called the economic dependency ratio9.
  1. Dependent or dependant, n. - dependent, adj. - dependency or dependancy, n.: the state of being dependent.
  2. The ratio of the young and the elderly to the adult population is called the age dependency ratio.


It is possible to classify the population by the sector of economic activity from which they derive their livelihood, dependants being put into the same category as their breadwinners. We speak of the population dependent on1 a particular branch of activity and in particular of the population dependent on agriculture2. The term agricultural population2 is sometimes used as a synonym, but may also be employed in the sense of farm population2 which lives on farms or is dependent on agriculture and which is distinguished from the non-farm population3 or non-agricultural population3.


The infirm1 or handicapped1 are often separately shown in censuses. They are classified according to the nature of their infirmity2 or handicap2. Physical infirmities3 or physical handicaps3 such as blindness, or deaf-mutism are generally distinguished from mental infirmities4 or mental handicaps4, such as feeblemindedness or dementia.


The study of the working life1 of individuals includes the study of the accession to the labor force2 and of the separation from the labor force3. At accession it is possible to distinguish those who have never been active, from those who belonged to the labor force at an earlier date; separations may be listed by cause, e.g. death, retirement4, temporary withdrawal. The analysis may proceed by cohort or period, and it involves rates of accession to the labor force5, or probabilities of accession to the labor force6, rates of separation from the labor force7 or probabilities of separation from the labor force8, eventually by cause; these indices are computed by age or age-group.


These indices serve to compute tables of working life1, by period or cohort. In addition to the probabilities described in the previous paragraph, these tables contain the distributions by age at accession to the labor force2 and by age at separation from the labor force3, (eventually by cause, before and after accounting for mortality), the mean age at accession to the labor force4 and the mean age at separation from the labor force5. The expectation of working life6, the gross expectation of working life7 (which excludes the effect of mortality) and the net expectation of working life8 (which includes it) all represent the mean number of years of working life that remain to be lived at each age by the active population. For those entering the labor force at that age, this expectation constitutes the mean duration of working life9; a similar index can be computed for all ages at accession taken together.
  1. Such tables are computed when temporary withdrawals from the labor force are a negligible proportion of the total, and this condition is approximately realized for males. For females, it is necessary to distinguish first accession to the labor force, or entry into the labor force, from re-entry into the labor force.

Chapter 4 • Mortality and morbidity


The study of mortality1 deals with the effect of death on the population. The general terms mortality rate2 or death rate2 encompass all the rates (133-4) which measure the frequency of deaths3. Where the expression death rate is used without any qualifying adjective the crude death rate4 is usually meant (cf. 136-8 for a general discussion of crude rates). This is generally an annual rate and consists of the ratio of the annual number of deaths occurring during a calendar year to the number exposed to the risk of dying during the same period. This number is equivalent to the mean population5 or average population5 for the period, and the population at the mid-point of the period can usually be substituted for the average population without appreciable error, if the size of the population is changing fairly uniformly. If the mortality of a sub-population (101-6) only is studied, we speak of specific death rates (134-6) among which sex-age-specific death rates6 are the most common. Age specific death rates7 without distinction of sex are also used on occasion.
  1. Occasionally the term mortality is used as a synonym for mortality rate or death rate.
  2. Death, n. - die, v. - dead, adj. syn. - deceased, adj. or n.
  3. When the observation period exceeds one year, the mean population is generally obtained as the average of several estimates of the size of the population for each year. The average number of persons years (135-6) is also used as denominator.


Specific death rates may be used to study differential mortality1 or mortality differences1 between groups, and reference is made to an excess mortality2 of one group as compared with another, or with the rest of the population. It is measured by an excess mortality index3★. The study of differences in the death rates of specific occupations is called the study of occupational mortality4. In a rather different sense the term occupational mortality5 may refer to the mortality from hazards associated with a particular occupation. Among these, we may mention occupational diseases6.
  1. Differentials in mortality is also encountered.
  2. The expression excess male mortality implies a comparison with the corresponding female mortality, e.g. at the same age.


Crude death rates (401-4) will depend upon the structure [particularly the age structure (325-6)] of the population as well as on the level of mortality. If the mortality of different populations is to be compared standardized mortality rates1 or adjusted mortality rates1 are sometimes computed to eliminate the effect of differences in population structure (144-4). Age is the characteristic for which mortality rates are adjusted most frequently by reference to a standard population2 with a given structure. If specific rates (134-6) for the population studied are available, it is possible to use the direct method of standardization3 which consists of applying these rates to the corresponding groups of the standard population. If specific rates are not available, it is still possible to obtain standardized mortality rates by the indirect method of standardization4. More frequently, comparative mortality indices5 are computed by applying standard mortality rates6 to the different groups of the population studied and summing these to obtain an expected number of deaths; the indices are then obtained by comparing the observed deaths7 in the population with the expected deaths8 which would have occurred had the standard rates applied.
  1. Standardize, v. - standardized, adj. - standardization, n.: the process of standardizing.
  2. If a crude death rate (401-4) is multiplied by a comparative mortality index, we obtain an indirectly standardized death rate. In British official terminology, when occupational mortality is studied, the figure obtained by direct standardization is called a comparative mortality figure and that obtained by indirect standardization a standardized mortality ratio.


The mortality of live-born children who have not yet reached their first birthday is called infant mortality1. The mortality of live-born children who die before reaching a certain age taken as four weeks or 28 days, the so-called neo-natal period3, is called neo-natal mortality2. The mortality during the first week of life and between the first week until before 28 days are called respectively early neo-natal mortality4 and late neo-natal mortality6★. The term post-neonatal mortality5 refers to deaths after the neo-natal period, but before reaching the age of one year.
  1. In certain statistics the neo-natal period is defined as the first month of life. The term early infancy is occasionally used as an approximate equivalent to the neo-natal period, as, e.g., in "diseases of early infancy."


The expression foetal mortality1 is used for deaths prior to the complete expulsion or extraction from its mother of a product of conception (602-6) irrespective of the duration of pregnancy (603-3). The terms intra-uterine mortality1 or mortality in utero1 may also be used. The corresponding deaths are called foetal deaths2 or intra-uterine deaths2. Early foetal mortality3 occurs before the twentieth week of gestational life, while intermediate foetal mortality4 occurs between the twentieth and the 28th week of gestation. After the twenty-eighth week, one refers to late foetal mortality5 and the product is called a late foetal death5 or, popularly, a stillbirth5. Perinatal mortality6 includes late foetal mortality and a portion of infant mortality that may include either early neo-natal deaths, or all neo-natal deaths. The foeto-infant mortality7★ includes stillbirths and deaths of children under one year.
  1. Foetal - also spelled fetal.
  2. Also designated as pregnancy wastage. These terms include abortions (603-5), miscarriages (604-1) and stillbirths.
  3. Early foetal deaths are also popularly known as miscarriages.
  4. Stillbirth, n. - stillborn, adj. In certain countries, including France, children born alive who died before registration may be legally included among the stillborn, and are called false stillbirths.
  5. The corresponding deaths are called perinatal deaths.


The ratios of deaths under one year of age1, of deaths of less than 28 days, and of deaths of less than one week, occurring in a year, to the number of live births of the same year give respectively the infant mortality rate2, the neo-natal mortality rate3 and the early neo-natal mortality rate4. These rates are generally expressed per one thousand live births. When deaths are cross-classified by age and year of birth, it is possible to divide the deaths under one year by the births in the two cohorts to which they belong. The resulting index is an adjusted infant mortality rate5 equivalent to a probability of dying before age one5. In the absence of such information separation factors6 may be estimated, which divide infant deaths into those occurring to infants born in the current calendar year and to infants born in the previous calendar year.


The proportion of late foetal deaths (411-5) among all births is called a late foetal mortality rate1. The ratio of late foetal deaths to live births (601-4) is called a late foetal mortality ratio2. A foetal mortality rate3 represents the number of known intra-uterine deaths per one thousand births in the same year while the foetal mortality ratio4 is the ratio of intra-uterine deaths to live births in a given year. These indices greatly understate intra-uterine mortality since early intra-uterine deaths frequently remain unobserved or unknown. A better measurement of intra-uterine mortality is provided by intra-uterine mortality tables5, a specialized application of the life table (cf. 432) which takes into account the duration of gestation. The perinatal mortality rate6 relates perinatal deaths (411-6*) to the sum of late foetal deaths and live births. The foeto-infant death rate7★ represents the number of known stillbirths and deaths in the first year of life per one thousand live births and stillbirths of the same reporting period.
  1. Also called stillbirth rate. This usage is not recommended.
  2. Also called stillbirth ratio. This usage is not recommended.
  3. The perinatal mortality ratio relates perinatal deaths to live births only.


In the study of age-specific mortality1, the terms infant mortality (410-2) and neo-natal mortality (410-3) refer to generally accepted time periods. The usage of such terms as child mortality2, youth mortality3★, adult mortality4 or mortality of old age5 is not uniform. Post-infantile child death rate6 sometimes refers to the death rate between one and 4 years of age.


The study of morbidity1 deals with the investigation of illness2, sickness2, ill-health2 or disease2 in a population. Two aspects are considered: the incidence of disease3 and the prevalence of disease4 according to whether the new cases of disease5 are considered or the number of cases existing at one point in time. The compilation of morbidity statistics6 is hampered by the lack of a sharp distinction between health and the morbid state7. Nosology8 and nosography9 contribute respectively to the classification and description of diseases.
  1. Disease, illness, or sickness are used as collective nouns in the singular, or both in the singular or plural to designate specific ailments.


Health statistics1 encompass morbidity statistics, but also cover all aspects of the health of a population, and are generally taken to include statistics of cause-specific mortality2. The classification of deaths by cause of death3 is made difficult because in many cases there may not be a single cause of death4 but multiple causes of death5 or joint causes of death5. When this is the case we may distinguish between the immediate cause of death6 and the underlying cause of death7 or, looking at the problem from a different point of view, we may distinguish between the primary cause of death8 or principal cause of death8 and the secondary cause of death9, contributory cause of death9 or associated cause of death9. The cause-specific death rate10 is generally expressed per 100,000 population. The ratio of the number of deaths from a specific cause to the number of deaths from all causes is referred to as the cause-specific death ratio11. Such ratios calculated for specific age groups or the general population provide information of the underlying structure of causes of death12★.


Death or disability (426-2) may be the consequence of disease (420-2) or of injury1 or poisoning2. Injuries may be due to accident3 or violence4. Among cases of violence it is normal to distinguish suicides5 and attempted suicides5, homicides6 and deaths or injuries due to operations of war7.
  1. Accident, n. - accidental, adj.
  2. Violence, n. - violent, adj.
  3. Homicide, n.: May in law be murder or manslaughter.
  4. Abbreviated to war deaths and war injuries.


An endemic disease1 is one that permanently affects substantial segments of a population, in contrast with an epidemic2, which spreads and then disappears within a fairly short time; when it appears in a large number of countries, it is called a pandemic3. Certain infectious diseases4 or communicable diseases4 have attracted particular attention, because they are capable of infecting large numbers of persons within relatively short time intervals. In such instances we speak of epidemic diseases5, and special epidemiological statistics6 are collected to show their incidence. It is possible to obtain information about these illnesses in various countries because legislation has made their reporting compulsory; they are therefore called notifiable diseases7. A distinction is sometimes made between chronic diseases8 and acute diseases9. These terms are not precisely defined, but acute diseases are generally understood to be those of abrupt onset and short duration while chronic diseases are those with slow onset and long duration, and often causing prolonged disability.
  1. Epidemic, n., also used as adj.
  2. Infectious, adj. - infect, v. - infection, n. The terms communicable diseases, contagious diseases and infectious diseases are not synonymous. A contagious disease can only be transmitted from person to person; thus, malaria, a communicable disease, is not contagious. Moreover, certain infectious diseases are not communicable.
  3. Epidemiology, n.: the science dealing with epidemics - epidemiologist, n.: a specialist in epidemiology - epidemiological, adj.: pertaining to epidemiology. The meaning of these terms has expanded greatly, and epidemiology now covers the study of relations between a biological or medical phenomenon and various factors, such as tobacco for example in "the epidemiology of lung cancer," or alternatively the statistical analysis of geographic variations in health phenomena.


Demographers devote particular attention to certain aspects of mortality: endogenous mortality1 which results from the genetic constitution of the individual, congenital malformations2, injuries connected with birth, or degenerative diseases associated with aging; exogenous mortality3, in contrast, results from external causes such as infectious or parasitic diseases and accidental injuries other than those incurred by the child during birth. Also of special interest are diseases connected with pregnancy, labor and the puerperium4. Mortality from these latter diseases is called maternal mortality5, and a maternal death rate6 may be computed as the ratio of maternal deaths in a year to the births of the same year. The proportion of deaths due to senility7 has mostly drawn interest as an index of poor reporting of causes of death.
  1. Infant mortality (410-1) can thus be decomposed into endogenous infant mortality and exogenous infant mortality.
  2. See note 1.
  3. The puerperium is the lying-in period following a birth, and the mortality of mothers during the period is called puerperal mortality.
  4. Senility n. - senile, adj.


Three aspects of morbidity (420-1) are commonly measured by morbidity rates1 or morbidity ratios1: frequency, duration and severity. These indices may be computed for specific diseases, or for all diseases. Two indices of the frequency of ill-health are the incidence rate2, the number of new cases of disease during the period related to the average population, and the prevalence rate3, the number of cases existing at a given moment of time expressed per unit of the average population. Either the average duration per case4, or the disability rate5, which is the mean number of days of illness5 per person in the population, may serve as a measure of the duration of illness. The case fatality rate6, which is the proportion of fatal cases among the reported cases of the specified diseases, may be used as an index of severity.
  1. This is said to measure the lethality of the disease.


An impairment1 refers to any physical, functional or psychological defect, which results from illness, injury or congenital malformation. When an impairment inhibits an individual’s ability to work or participate in normal activities it is referred to as incapacity2 or disability2. This may be total or partial; in either case, permanent disability3 or infirmity4 refer to an irreversible condition which gives rights to professional incapacity7★ or work incapacity8★ compensations. The probability that a healthy individual aged exactly x years will become disabled in the next year or over the course of some number of years starting with this exact age, is called the risk of disability5 or the probability of disability5. A series of these probabilities can be combined into a disability table6, which is a specialized extension of the life table (cf. §432). It give rights to Professional incapacity or occupational disability


Mortality statistics are generally compiled from death registration (cf. 211). When a death takes place a death certificate1 is generally issued; statistics are compiled from the information given on death certificates. In some countries a distinction is made between the medical certificate of death2 issued by a medical practitioner who has attended the deceased person during his or her last illness, and an ordinary death certificate issued by the registrar of deaths for legal purposes.
  1. The first death statistics in England and Wales were compiled from bills of mortality which were generally drawn up on the basis of burial registers. In countries where vital registration is deficient, statistics can be gathered by the survey technique; questions may be asked on deaths during a reference period, generally the previous year; the indirect estimation of mortality relies on such question as the number of children surviving among children ever born (637-2), orphanhood status or widowhood status.


Probabilities of dying1 or death probabilities1 are used to study in detail the mortality of a period or of a cohort. They are the probabilities that an individual of exact age x will die before exact age x + n, and are represented by the symbol nqx. If n = 1, we talk about annual death probabilities2; if n = 5, about quinquennial death probabilities3. The instantaneous death rate4, or as it is occasionally called the force of mortality4, is the limit of the nqx value as n tends to zero. The projective mortality probability5★ is the probability that individuals of the same cohort or group of cohorts died between two January 1st. The name of this probability comes from its use in the calculation of population projections. The complement to one of the probability of dying from exact age x to exact age x + n is the probability of survival6 over this interval. In the preparation of population projections, we use survival ratios7; they represent the probability that individuals of the same birth cohort or group of cohorts will still be alive n years later.
  1. The probability of death between age x and x + n is defined as the ratio of deaths between ages x and x + n to the number of survivors at exact age x. It is not to be confused with the central death rate, the ratio of deaths between ages x and x + n to the mean population alive at that age. The central death rate is written nmx .
  2. The probability of survival from age x to age x + n is written npx .


The course of mortality throughout the life cycle may be described by a life table1. A life table consists of several life table functions2, all of which are mathematically related and may be generally derived when the value of one of them is known. The survivorship function3 shows the number of survivors4 of a cohort (116-2) of births to various exact ages (322-7) on the assumption that the cohort is subjected to the rates of mortality shown. The number of births in the original cohort is known as the radix5 of the life table and the process by which the original cohort is reduced is known as attrition6.
  1. The number of survivors to exact age x is denoted by lx .
  2. The radix is usually a power of 10: 10,000 or 100,000 for example.


To the survivors function corresponds a death function1 which is calculated as the differences between the number of survivors (432-4) at different ages within the given age interval. It is named the distribution of life table deaths2★ in order to be distinguished from the crude distribution of deaths. Life tables typically include the expectation of life3 or life expectancy3 at age x ; this is the mean number of years to be lived by those surviving to exact age x, given the mortality conditions of the table. The expectation of life at birth4 is a particular case of expectation of life, and represents the mean length of life4 of individuals who have been subjected since birth to the mortality of the table. The reciprocal of the expectation of life at birth is the life table death rate5 or death rate of the stationary population5.
  1. By integrating the survivorship function (432-3) between two exact given ages we obtain the total number of years lived by the cohort between these ages; the notation for the total number of years lived between age x and x + n is nLx . This function is often called the stationary population in life table column headings. By summing it from a given age x to the end of life, we obtain the total number of years to be lived after attaining age x by those reaching that age; the conventional notation is T x .
  2. The notation for the expectation of life at age x is ex


The median length of life1 sometimes called the probable length of life1 is the age at which half the original cohort of births have died. After infancy the distribution of deaths by age in the life table will usually have a mode and the corresponding age is called the modal age at death2, or sometimes the normal age at death2. It may be of interest as an indicator of human longevity3 or the length of life3 corresponding more closely to the sense in which the term is used in everyday language than either the average (433-4) or the median length of life. The term life span4 is used to refer to the maximum possible length of human life.


A complete life table1 is usually one in which the values of the life table functions (432-2) are given in single years of age. An abridged life table2 is one in which most functions are given only for certain pivotal ages, frequently spaced at five or ten year intervals after infancy; intermediate values for the functions are usually obtained by some form of interpolation (151-7). The term life table for selected heads3 is used to refer to a life table relating to the experience of a number of specially selected individuals, such as the clients of a life insurance company, in opposition to general life tables4 which relate the experience of a whole population (101-4). Life tables are generally presented on a sex-specific basis although on occasion they are presented for both sexes. A life table which is based only upon the generalization of empirical relationships is called a model life table5.


A calendar-year life table1 or period life table1 (cf. 153-2; 432-1) is one in which the mortality rates used relate to a specified time interval and the cohort (116-2) is therefore hypothetical. A generation life table2, or cohort life table2 on the other hand, traces the experience of an actual birth cohort and the mortality rates contained in the table are then spread over a prolonged period, usually about 100 years. A mortality surface3 is drawn when probabilities of dying (431-1) are plotted against age and time period simultaneously in a three-dimensional diagram.


The Lexis diagram1 is commonly used to illustrate the usual method for computing death probabilities and other demographic measures. In this diagram, every individual is represented by a life line2 which begins at birth and ends in the point of death3. A method for the study of mortality at very advanced ages has been called the method of extinct generations4, because it uses observed deaths for cohorts which have been completely eliminated by mortality.

Chapter 5 • Nuptiality


The study of nuptiality1 deals with the frequency of marriages2 i.e. of unions3 between persons of opposite sexes which involve rights and obligations fixed by law or custom; with the characteristics of persons united in marriage; and with the dissolution of such unions. By extension, it also includes the study of other conjugal unions (503-8) where their frequency makes their inclusion necessary. A marriage4 or wedding4 is the ceremony, prescribed by law or custom, which establishes such a union between a man and a woman as spouses5, i.e. husband6 and wife7. The spouses jointly are called a married couple8.
  1. Marriage, n. - marry, v. - married, adj. - marriageable, adj.: capable of contracting a marriage.
  2. A man at, or soon before or after his marriage, is a bridegroom (abbreviation: groom).
  3. A woman at, or soon before or after her marriage, is a bride.


Marriage laws1 or marriage customs2 differ in different societies. A society in which a person may be married to only one person of the opposite sex at a time is called monogamous3. Societies in which a person may be married to several persons simultaneously are called polygamous4. A distinction is made between polyandrous5 societies, where a woman may have several husbands, and polygynous6 societies, where a man may have several wives. The term "polygamy" is frequently used in the sense of polygyny.
  1. Monogamous, adj. - monogamy, n.
  2. Polygamous, adj. - polygamy, n.
  3. Polyandrous, adj. - polyandry, n.
  4. Polygynous, adj. - polygyny, n.


In some countries a legal union can be established only through a civil marriage1 performed by an official of the state; in other countries a religious marriage2 in accordance with the regulations of a church is recognized as having legal force. Social or legal recognition may be given under various conditions in different countries to stable unions which have not been solemnized by a legal or religious ceremony, for instance to customary marriages3 or to common law marriages3 conforming to local traditions. Different types of relationships and degrees of social acceptance are implied in terms applied to various unions but their significance varies widely in different countries. The term consensual union4 implies a socially recognized stable union, the term companionate marriage4 has a similar connotation. The terms free union5 and temporary union6 both imply a less stable union that may or may not include cohabitation7. Two persons of opposite sexes living in a stable union, whether legal or not, are called a couple8. The term conjugal union8 has been used by demographers to include both legal unions and more or less stable illegal unions.
  1. Concubinage, n.: a type of illegal union. A concubine in the restricted sense is a woman with an accepted conjugal status inferior to that of a legally recognized wife, particularly in polygynous societies. In other societies, the word concubine is sometimes used loosely to denote any woman other than a wife living in conjugal union with a man. Today such terms as companion or mate are preferred.
  2. Cohabitation, n.- cohabit, v.


In many countries a minimum age at marriage1 is laid down by law. The age differs from country to country and may be different for the two sexes. Marriages among persons closely related by blood are called consanguineous marriages2 and are generally prohibited by either law or custom. Persons who are forbidden to marry one another for these reasons are said to be within the prohibited degrees of consanguinity3.


In some countries the publication of banns1 or intent to marry1 is a necessary preliminary to a marriage (501-4), giving public notice to persons interested, who may then oppose the marriage if they have reason to do so. In many countries a marriage license2 must be obtained before the marriage ceremony can take place. A marriage certificate3 is usually delivered to the newly married couple4 after the ceremony. The consummation of marriage5 has occurred, or a marriage has been consummated5 when sexual relations have taken place between the spouses.
  1. Before the celebration of the marriage the future spouses are said to be engaged or betrothed, words which come from the custom of engagement or betrothal which consists of a more or less formal exchange of promise to marry.


Endogamy1 exists where both spouses must belong to the same group (e.g. tribe, clan). The term is also used to denote a tendency for spouses to be members of the same social or geographical group or isolate2, which is generally of limited size. The opposite requirement or tendency is called exogamy3. Mixed marriages4 are marriages between persons of different nationalities, races, religions, etc. When marriage is contracted between persons with certain common characteristics, social, physical or mental, it is called homogamy5, the opposite is called heterogamy6.
  1. Endogamy, n. - endogamous, adj.
  2. Exogamy, n. - exogamous, adj.
  3. Homogamy, n. - homogamous, adj.
  4. Heterogamy, n. - heterogamous, adj.


At the close of married life1 or conjugal life1, the end of union2 coincides with the dissolution of marriage3, i.e. the breaking of all legal obligations resulting from the status of spouse, including the removal of legal obstacles to a new marriage. If a marriage is dissolved by death the surviving spouse is called a widower4 if male and a widow5 if female. Widowed persons6 live in a state of widowhood7.


Where divorce1 as an institution is recognized, the dissolution of marriage (510-2) may take place through the granting of a decree of divorce2 to one of the spouses. In some countries a spouse may be repudiated3 by the other. Persons whose marriages have been dissolved by divorce are called divorced persons4. The French words divorcée (fr)6 (woman) or divorce5 (man) are sometimes used in English, though the masculine form is rare.
  1. Divorce, n. and v.


In some countries the principle of the indissolubility of marriage1 is upheld by law or custom and divorce (511-1) is not allowed; only the death of one of the spouses (501-5) may bring about dissolution of the marriage (510-3). Under any legal system, however, lack of harmony may lead to separation2 of the spouses. This may take the form of a de facto separation3, either through common consent or as the result of the desertion4 of one of the spouses by the other. Or it may take the form of a legal separation5 or judicial separation5. A judicial separation absolves the parties from certain obligations, including the duty of living together, or cohabitation, but does not enable either of them to contract a new marriage. Persons whose marriages have been broken by separation are called separated persons6. Marriages in which the spouses no longer cohabit but which have not been legally dissolved may be called broken marriages7.


A decree of nullity1 or an annulment of marriage1 is a declaration by a court of law that, although a marriage ceremony has taken place, there has been no valid marriage2. The expression dissolved marriage3 is frequently understood to include cases of annulments and of legal separation, although legally the marriage is not dissolved. The term end of union (510-2) is more appropriate than dissolution in such cases and may also refer to unions other than marriage.


From a legal point of view, any person who meets the conditions set by law or custom to contract a marriage is marriageable1, and the marriageable population2 is made up of such persons; the non-marriageable population3 consists of those who are not free to do so by law or custom. The marriage market4, the marriageable circle5★ or group of persons5★ among whom mate selection6 takes place however, does not include all marriageable persons; candidates to marriage7 include only those who are not excluded, at least temporarily, by reasons of health or other circumstances from the marriage market. Widowed or divorced persons may contract a new marriage; there is thus a distinction between a first marriage8 and a marriage of higher order, or remarriage9. Because the order of marriage10 may differ for the two spouses, the term “first marriage” is ambiguous unless specified as referring to groom (501-6*) or to bride (501-7*) or to both parties; unless otherwise specified, it refers to a marriage between a bachelor (515-3) and a spinster (515-4).
  1. Remarriage, n. - remarry, v. - remarried, adj.


The population may be divided into different groups by conjugal status1, marital status1 or marital condition1. Single2 persons, bachelors3 (men) and spinsters4 (women), are those who have never been married; they are also sometimes called the never-married2 class. The class of married persons5, married men6 and married women7, consists of those who have been married and whose marriages have not been dissolved (513-3). All persons except single persons are ever-married persons8.
  1. A synonym is celibate, adj. - celibacy, n.: the state of being single.


Relative marriage frequency is measured by marriage rates1 or nuptiality rates1, among which the crude marriage rate2 gives the ratio of the total number of marriages to the total population in a given period. Male nuptiality3 and female nuptiality4 are often different, and can be studied separately. The terms male nuptiality and female nuptiality are used for the marriage frequency of the different sexes. A sex-specific marriage rate5 can be computed with the appropriate population of each sex as a base. It is usual to distinguish between a first marriage rate6, which relates the number of bachelors or spinsters (515-3 and 4) marrying to the total number of bachelors and spinsters respectively and a remarriage rate7 which relates the number of remarriages to the total number of widowed and divorced persons. Similar rates can be computed by age or age-group of husband and wife whenever marriages are classified by age at marriage8 of each spouse; such rates are called age-specific marriage rates9. The tabulation of spouses by age at marriage permits the computation of the mean age at marriage10 or average age at marriage10 for the given year or period. Age differences between spouses11 can be analyzed from a classification of the combined ages12 of the spouses.
  1. Sometimes the crude marriage rate is obtained by relating the number of newly married persons to the total population.
  2. The terms marriage frequencies and first marriage frequencies have sometimes been used to refer to the ratio of the number of marriages or first marriages at a certain age, to the total number of persons of that age, irrespective of their marital status. Cumulated marriage frequencies and cumulated first marriage frequencies are used in cohort studies.


The prevalence of marriage in a generation of men or women is measured by the proportion never married1. This is usually equivalent to the proportion remaining single2 at an age such as 50 after which first marriages are rare. The proportion remaining single at each age in a cohort can be computed from first marriage probabilities3, i.e. the proportion of single persons at exact age x who will marry before exact age x + 1, assuming that there is no mortality. For practical purposes, however, the proportion remaining single is usually obtained from census data as the proportion single4 at that age in the corresponding cohort. When a classification of first marriages by age of the spouses is available the mean age at first marriage5, the median age at first marriage6 and the modal age at first marriage7 can all be computed. In the absence of data on the timing of marriages, it is often possible to compute a singulate mean age at marriage8 from census data on the proportions single by age.


Nuptiality tables1 resemble life tables, and combine various nuptiality functions. The gross nuptiality table1 includes, by age, the first marriage probabilities (521-3) and proportions remaining single (521-2), as well as the number of first marriages2 in a cohort of given size subjected to the prevailing nuptiality on the assumption that there is no mortality; it also gives the numbers remaining single3 at various ages. The net nuptiality table4 takes mortality as well as nuptiality into account, and is a particular case of double decrement tables (153-4). Such a table includes the single survivors5, the ever-married survivors6, the probability of single survival7 and the expectation of unmarried life8.


A divorce rate1 can be calculated in different ways. The crude divorce rate2 gives the ratio of the number of divorces to the average population during a given period. The ratio of divorces to the number of married couples is sometimes computed and may be called the divorce rate for married persons3. If divorces are tabulated by the age of the divorced person or by duration of marriage, age-specific divorce rates4 and duration-specific divorce rates5 can be computed. Another index of divorce frequency is obtained by computing the number of divorces per new marriage6.
  1. This is a period measure which relates the divorces of one year, either to the marriages of that year, or to a weighted average of the marriages of several years. In cohort analysis, it is possible to relate divorces in successive years to an initial marriage cohort to compute the cumulated proportion divorced.


When the requisite basic statistics are available, marriage dissolution probabilities1 may be computed, showing for each sex the probability of the marriage being dissolved by death or divorce according to duration of marriage2; marriage dissolution tables are an application of double decrement life tables. Remarriage tables for widowed and divorced persons can also be computed, but the most common indices of remarriage are the relative frequency of remarriage3, i.e. the proportion of widowed or divorced persons who remarry, often given by age at widowhood or divorce, and by the interval between widowhood or divorce and remarriage. The latter information enables one to compute the mean interval between widowhood and remarriage4 and the mean interval between divorce and remarriage5.

Chapter 6 • Fertility


Demographic studies of fertility1 deal with certain phenomena connected with human childbearing2 or reproduction2. The term natality1 is sometimes used instead of fertility. These terms refer to the frequency of occurrence of births3 or more specifically live births4 — within populations and sub-populations. A birth is the process of delivering a child. Live births or the births of live-born children5 are distinguished from late foetal deaths (cf. 411-5) by evidence of life, such as respiration, movement of voluntary muscles or heartbeat of the child after complete expulsion or extraction. The term effective fertility6, which was once used to indicate that late foetal deaths were not counted among the total number of births, should refer to the cases in which the deaths of infants or children are excluded from consideration. The term crude fertility7★ should refer to all births including stillbirths (411-5) or foetal deaths. The term differential fertility8 designates fertility differences between the subgroups of a population.
  1. On the meaning of the term fertility in demography, see also § 623.
  2. Reproduction, n. - reproduce, v. - reproductive, adj. Frequently, reproduction refers to the balance of births and deaths (as in § 711) rather than to the process of childbearing or procreation.
  3. The word birth is now commonly used to mean live birth.
  4. Live-born, adj. also used as noun to mean: infant born alive.


Conception1 results from the fertilization2 of an ovum3 by a spermatozoon4 or sperm cell4 and marks the beginning of pregnancy5 or gestation5 for the impregnated woman. In the course of its development the product of conception6 is successively called an embryo7 and then a foetus7 — sometimes written as fetus7. The moment at which the embryo becomes a foetus is not precisely determined: certain scientists set it at the end of 12 weeks or three months of intra—uterine life, although successive developmental stages after the eighth week are often termed foetal. Nidation8 refers to the implantation of the egg in the wall of the uterus9 or womb9, a process which occurs a few days after fertilization.
  1. Conception, n.- conceive, v.
  2. Fertilization, n. - fertilize, v.
    Artificial fertilization: fertilization obtained by artificial insemination, i.e. by a process other than coitus (627-2).
  3. A fertilized ovum is called an egg or zygote.
  4. Pregnancy, n. - pregnant, adj.: gravid, expectant. Certain scientists consider that a pregnancy begins only at the time of nidation (602-8) of the egg.
  5. Embryo, n. - embryonic, adj. - embryology, n.: the science dealing with the development of the embryo.
    Foetus or fetus, n. - foetal or fetal, adj. (cf. 411).
  6. Uterus, n. - uterine, adj.


A foetus is said to be non-viable2 during the first part of a pregnancy and viable1 thereafter. The change occurs when the foetus becomes capable of independent existence outside its mother, which is commonly considered to take place when the period of gestation3 or duration of pregnancy3 has exceeded 28 weeks. If the pregnancy has lasted longer than this, the expulsion of the foetus (alive or dead) takes place during confinement4; an earlier explusion associated with an early foetal death is called an abortion5 (cf. § 604). The period of about six weeks after delivery (during which the uterus usually regains its normal size and in which the probability of conception is low) is called the puerperium6.
  1. Viable, adj. - viability, n.
  2. The minimum period determining viability varies between 20 and 28 weeks among countries, but the World Health Organization has recommended that 28 weeks be the standard time period. Generally the duration of pregnancy is computed from the onset of the last menses. This constitutes the conventional duration of pregnancy, as opposed to the true duration of pregnancy, computed from the time of conception.
  3. The actual process of expulsion of the foetus is called delivery or parturition, which is the termination of labor. In addition to those, confinement includes expulsion or removal of the placenta or afterbirth.
  4. Abortion, n. - abort, v.t. or v.i. - abortifacient, adj. used as n.: capable of inducing abortion. - abortionist, n.: a person who performs abortions. In everyday language, the term abortion often takes the meaning of induced abortion (604-2), as opposed to spontaneous abortion (604-1).
  5. Puerperium, n. - puerperal, adj. (cf. 424-4).


Abortions following a non-induced infra-uterine death, which may have occurred some time before expulsion, are called spontaneous abortions1 or miscarriages1, in contrast to intentional abortions2, or induced abortions2. A therapeutic abortion3 is one undertaken for medical reasons. The laws of certain countries permit abortions for health or other reasons; these are legal abortions4. Abortions which are induced contrary to law are called illegal abortions5 or criminal abortions5. According to the technique used, there are abortions by curettage6, abortions by vacuum aspiration7, abortions by dilatation and evacuation7, hysterotomies8 (involving surgical cutting into the uterus), and abortions by medical induction procedures9.
  1. Also called abortions by dilatation and curettage, (abbreviated to D and C).
  2. Also called abortions by suction. When the procedure is used very soon after a presumed conception, the terms menstrual regulation or menstrual extraction are used.
  3. Such procedures involve amniotic fluid exchange as in the instance of an abortion by saline injection, or the use of prostaglandins.


Full term deliveries1 occur when the pregnancy has lasted at least 37 weeks, measured in conventional duration of pregnancy (603-3*). A pregnancy ending before the normal period is termed a premature delivery2 or premature confinement2 or premature birth2 and the product of this delivery is called a premature baby4. Births which are not premature are called births at term3 or full-term births3. The word prematurity5 is used to refer to phenomena connected with premature delivery. A classification of births by stage of development that does not depend upon an estimate of the period of gestation is used in many countries. In this classification a live-born infant with a birth weight6 of 2,500 grams (5 1/2 lbs.) or less is said to be immature8. Immaturity7 is often combined with debility9, an abnormal state of weakness.


At most confinements there is a single birth1 or single delivery1 but at some there are plural births2, multiple births2 or multiple deliveries2. Two children born during the same confinement are called twins3 and we may distinguish between monozygotic twins4, uniovular twins4 or identical twins4 on the one hand, and dizygotic twins5 or biovular twins5 on the other. Monozygotic multiple births occur when one ovum splits after fertilization; the resulting children must always be of the same sex. Dizygotic multiple births are due to the simultaneous fertilization of two or more ova and the resulting children may be of different sexes.
  1. In British official terminology the term maternity is used to denote a confinement resulting in the birth of one or more children; the number of births per maternity may be computed.
  2. Where a multiple birth results in three children, these are-called triplets, four are quadruplets, and five quintuplets. The terms "twins", "triplets", etc. are generally used in accordance with the total number of deliveries during a confinement; occasionally, however, multiple births are classified only in accordance with the number of children born alive.


Births are classified by legitimacy1. Strictly speaking, a legitimate child2 may be defined as one whose father and mother were married to one another at the time of conception. But in practice, the classification depends upon the marital status of the mother at the time of the birth or, after the dissolution of marriage (510-3), at the time of conception. A legitimate birth3 is the delivery of such a .child; other births are illegitimate births4. It is general practice to consider as legitimate the children who result from pre-marital conceptions5 or pre-nuptial conceptions5 (i.e., conceptions occurring before marriage) provided that the parents are married to each other at the time of the birth. An illegitimate child6 or child born out of wedlock6 may be legitimized8 or legitimated8 by the subsequent marriage of its parents. The process of legitimation9, which varies in different countries, may confer on the illegitimate child some or all of the legal rights of legitimate children. In some legal systems it is possible for a father to grant recognition7 to, or acknowledge7, his illegitimate child, i.e., to admit in legal form that he is the child’s father.
  1. Bridal pregnancies is also used in this connection.
  2. The legal term bastard has acquired a derogatory meaning but is occasionally used by historical demographers. According to the law of some countries a child is illegitimate if it results from adulterous relations or extra-marital relations i.e., a connection between a married woman and a man other than her husband, but such a birth is not always registered as illegitimate.


Births are also classified by birth order1, e.g. first births, second births, etc. Birth order is usually determined by considering all previous births to the mother3, and sometimes only births of the present marriage2. Birth order is generally based on live births only, but occasionally late foetal deaths are taken into account as well. A classification of women by confinement order4 is made in the same way as for births by counting all pregnancies which lasted at least 28 weeks, and reckoning multiple births as one confinement (cf. 603-4). Similarly a classification by pregnancy order5 is made by counting all known pregnancies. In medical parlance, a woman is called nulligravida6 if she has never been pregnant; the terms primigravida7 and multigravida8 respectively are used for a woman who is pregnant for the first time or who has been pregnant before. Women are also classified by parity9, usually on the basis of the number of children born alive, although in biological literature the term refers to the number of confinements, and a woman who has had no confinement at all is said to be a nullipara10 or nulliparous10. Similarly, a woman is termed a primipara11 and deemed to be primiparous11 at her first confinement and a multipara12 or multiparous12 at subsequent confinements.
  1. Higher order births are births occurring after the last specified order, e.g. fifth and higher order births.
  2. A woman who has not borne any live children is called a zero-parity woman, a one-parity woman has borne one child but no more, and so on.


Studies of birth timing1 deal with the length of birth intervals2. These include the interval between marriage and the first birth3 and intervals between successive births4. The interval between a birth and a fixed date, such as that of a census (202-1 *) or survey (203-4), is called an open birth interval5; intervals that begin before and end after that date are called straddling intervals6. The interval between marriage and the Nth birth7 is also used to study the timing of births.
  1. Birth spacing, although sometimes found in the sense of birth timing as above, is commonly used to refer to the deliberate efforts of couples to postpone a birth.
  2. Also called first birth intervals. The second birth interval is that between the first and the second birth; and so on.
  3. As seen from the vantage of that census or survey, the intervals between the recorded successive births are called closed birth intervals.


In computing the period of exposure to the risk of conception1 it is necessary to consider pregnancy intervals2. The interval between marriage and the first pregnancy is the conception delay3 or first pregnancy interval3. The period between the end of one pregnancy and the beginning of the next is the inter-pregnancy interval4. If the time when the woman had no sexual activity is subtracted, a net inter-pregnancy interval5 is obtained. The period between the end of the last pregnancy and the date of a survey is called an open inter-pregnancy interval6.


The reproductive period1 (or in women the childbearing period1) begins at puberty2. Menstruation3 — the appearance of the periods4 or menses4 in women — also begins at puberty. The first period is called the menarche5 and menstruation ceases with the menopause6, which is also sometimes called the climacteric6. In practice, the reproductive period is often made to start, by convention, at 15 years or at the minimum age at marriage (504-1) and, for some, to end at 45 or 50 year. The temporary absence of menstruation, be it normal or pathological, is called amenorrhea7. Pregnancy amenorrhea8 occurs after a conception, and post-partum amenorrhea9 after a confinement.
  1. The terms reproductive ages or fecund ages are also used.
  2. Menstruation, n. - menstruate, v. - menstrual, adj.
  3. Menopause, n. - menopausal, adj. The expression change of life is used as a synonym for menopause in colloquial language.


The capacity of a man, a woman or a couple to produce a live child is called fecundity1. The lack of that capacity is called infecundity2 or sterility2; inability to conceive3 and inability to procreate10★ are the main, but not the single causes of sterility. Used alone, sterility usually carries the connotation of irreversibility, but occasionally temporary inability to conceive4★ and temporary sterility5 are distinguished from permanent inability to conceive6★ and permanent sterility7. Among women we distinguish primary sterility8 where the woman has never been able to have children, and secondary sterility9, which arises after one or more children have been born.
  1. Fecundity, n. - fecund, adj. An alternative meaning of the term implies the ability to conceive, rather than to produce a live child. The terms sub-fecundity and sub-fecund mean either that the capacity to produce a live child is below normal, or that the probability of conception is low.
  2. Sterility, n. - sterile, adj. Infecundity, n. - infecund, adj.


The term temporary sterility (621-5) is used even in instances where a woman’s inability to conceive is not the result of a pathological condition.Women are said to have sterile periods1 in each menstrual cycle2, because generally conception can occur only during a few days around the time of ovulation3. The period of sterility that extends from conception (602-1) to the return of ovulation after a delivery, which includes pregnancy (602-5) and is influenced by the duration of breastfeeding4, is called the nonsusceptible period5, particularly in mathematical models of reproduction. Temporary sterility is also used to refer to the occurrence of anovulatory cycles6 (i.e., menstrual cycles in which ovulation does not occur) or to abnormal periods of amenorrhea. The sub-fecundity7 of very young women is commonly called adolescent sterility8; it would be better to talk about adolescent sub-fecundity8.
  1. The period between delivery and the return of ovulation is often called the period of post-partum sterility.
  2. Also called anovular cycles.


Fertility1 and infertility2 refer to reproductive performance rather than capacity, and are used according to whether there was actual childbearing or not during the period under review. When it concerns the complete reproductive period, the term total infertility3★ may be used while permanent infertility4 may extend from a certain age or marriage duration to the end of the childbearing years. Voluntary infertility5★ is used when the absence of procreation corresponds to a decision of the couple (503-8).It should be noted that in many Latin languages, the cognates of fertility and fecondity are used in a sense diametrically opposite to that in English. Thus, the French fécondité and the Spanish fecundidad are properly translated by fertility, and fertilité and fertilidad by fecondity.
  1. Fertility, n. - fertile, adj.
  2. Infertility, n. - infertile, adj.
    Childlessness, n. - childless, adj. : refer to the state of a women, man or couple who have been so far infertile.


The fertility (623-1) of couples will depend upon their reproductive behavior1. A distinction is drawn between planners2, couples who attempt to regulate the number and spacing (612-1*) of their births, and non-planners3, couples who make no such attempt. Family planning4 has a broader meaning than family limitation4 which refers to efforts not to exceed the number of children wanted5. The terms birth control6 or fertility regulation6 are not restricted to the activities of married persons.
  1. A classification according to family planning status distinguishes couples who have not tried to regulate the number and spacing of their children from those who have tried to do so.
  2. Unwanted births or unintended births are those that occur after the total family size desired by the couple has been reached. They are distinguished from unplanned births that may have occurred at a time that was not intended, and perhaps outside of wedlock.


Family planning implies a concern with planned parenthood1 or responsible parenthood1, i.e., the desire to determine the number and spacing of births in conformity with the best interest of each couple, or of society. The number of children expected by a couple may differ from the desired number of children2 or intended number of children2 reported by the couple in a survey. Even if these goals are not revised, they may be exceeded as a result of contraceptive failures3 ; the frequency of the latter depends on contraceptive effectiveness4 which has two aspects. Theoretical effectiveness5 or physiological effectiveness5 indicates how reliable a method is when used all the time according to directions. Use effectiveness6 measures its reliability when used in everyday situations by a given population. Reasoning in terms of residual fecundability (638-7), use effectiveness is usually measured by the contraceptive failure rate7 which relates the number of unintended conceptions to the length of exposure to the risk of conceiving.
  1. In other terms, birth expectations differ from reproductive intentions. A distinction is made between desired family size, the number of children a woman, man or couple wants to have, and the ideal family size which they envision for their society. Intended family size may be lower than desired family size.
  2. Unplanned births are often opposed to planned births.
  3. 5. and 6. Efficacy is a synonym for effectiveness in these expressions.
  4. Not to be confused with the demographic effectiveness of a family planning program (see 626-7), or of a method in a population.


A family planning program1 seeks to introduce and diffuse birth control in a group of potential users2 or in a target population2. Teams of fieldworkers3, including canvassers3, motivators3 and distributors3, attempt to reach and convince the population to use contraception or abortion. The success of the program can be measured by the proportion of new acceptors4 in the target population, or by the acceptance rate4; for the acceptors of contraception, the continuation rate5 after a certain lapse of time and its complement, the termination rate6 or drop-out rate6 are also computed. Estimates of the numbers and proportions of births averted7 reflect the demographic effectiveness (625-4*) of the program. Contraceptive prevalence in a population is estimated by the proportion of current users8 of contraception from a relevant universe, such as married women of reproductive age.{
  1. Special surveys of knowledge, attitudes and practice of contraception have been called KAP surveys in abbreviation.


Contraception1 refers to measures which are taken in order to prevent sexual intercourse2 or coitus2 from resulting in conception; the term covers contraceptive sterilization (631-1). Birth control methods3 is used in a broader sense than contraceptive methods3 to include induced abortion (604-2). Abstinence4 from coitus, particularly periodic abstinence (628-4) is often included among contraceptive or birth control methods.
  1. Contraception, n. - contraceptor, n.: one who practices contraception. Contraceptive, adj. : used for contraception.
  2. Abstinence, n. - abstain, v.


A distinction is frequently drawn between appliance methods1 of contraception and non-appliance methods2. One principal non-appliance method of contraception is coitus interruptus3 or withdrawal3. Another non-appliance method of contraception is periodic abstinence4 or the rhythm method4, in which coitus is avoided during the period when the woman is believed to be fecund and takes place only during the so-called safe period5 of the menstrual cycle. The basal body temperature method6 refers to the method in which the woman keeps track of her temperature to identify the safe period.
  1. Appliance methods include not only barrier methods which are used to prevent the union of the sperm and ovum, but also methods using other contraceptive devices such as the intra-uterine device (629-10) and other types of contraceptives such as the pill (630-4).
  2. The term natural family planning methods has been applied collectively to cover the rhythm method, the basal body temperature method, and other techniques which attempt to identify stages of the woman’s ovulatory cycle.


The barrier methods which are more commonly used alone or in combination include the condom1 or sheath1, used by men, and the cervical cap2 or pessary2, the diaphragm3, tampon4 or sponge4, contraceptive jelly5, suppository6, foam tablets7 and douche8 with or without spermicide9, used by women. There are various types of intra-uterine devices10 (abbreviated to IUD10), including the loop10, the coil10, the copper T10, etc.


Oral contraceptives1 are a method of hormonal contraception2 or contraception by steroids3. These inhibit ovulation by regular ingestion of the pill4, or by injections or implants.


Sterilization1 results from various surgical procedures: on the male, vasectomy2 or occlusion3★ involves tying and cutting the vas deferens; on the female tubal ligation4 and salpingectomy5 or tubectomy5 involve interventions on the fallopian tubes. Hysterectomy6 or excision of the uterus, also involves sterilization of the woman.
  1. and 5. Various procedures are used to gain access to the Fallopian tubes, such as laparotomy, colpotomy or laparoscopy.


The general term birth rate1 refers to a rate calculated by relating the number of live births observed in a population or sub-population during a given period to the size of the population or sub-population during the period. The rate is usually stated per 1,000, and the most usual period is one year. Where the term birth rate is used without qualification, it is understood to be the crude birth rate2, and all live births are related to the entire population. The total birth rate3 based on live births and late foetal deaths is sometimes calculated. Legitimate birth rates4 and illegitimate birth rates5 are also calculated with legitimate and illegitimate births in the numerator and the currently married and unmarried female population, respectively, in the denominator. The illegitimacy ratio6, the number of illegitimate births per 1,000 total births, is more frequently used, however. To compare the fertility of different populations, standardized birth rates7 are often used to eliminate the effect on the birth rate of certain differences in structure of the population (most commonly the age and sex structure). The child-woman ratio8, most commonly the number of children aged 0 to 4 per 1,000 women of childbearing age, e.g., 15 to 49, is used as an index of fertility when reliable birth statistics are not available.
  1. The denominator of the legitimate and illegitimate birth rate is sometimes the total population.
  2. See note 4.


The term fertility rate1 is often used when the denominator of the birth rate fraction is restricted to a group of individuals of the same sex in the reproductive ages (620-1). This denominator is commonly the mid-year population in the stated period, but it may also be the number of years lived by the group during the period, or the mean size of the group. Unless otherwise indicated, these rates are female fertility rates2, and the rates are calculated for groups of women; the number of years lived by a given number of women in an interval is called the number of woman years3. Male fertility rates4 are computed sometimes in an analogous manner. Fertility rates are generally expressed as births per thousand (implied: individuals of the same category — sex, age, marital status, etc. — cf. 133-4*). Marital fertility rates5 or legitimate fertility rates5 relate the total number of legitimate births (610-3) to the number of currently married women; non-marital fertility rates6 or illegitimate fertility rates6 relate the total number of illegitimate births (610-4) to the number of single, widowed and divorced women. Overall fertility rates7 make no distinction according to the legitimacy (610-1) of the births or the marital status of the parents. The general fertility rate8 relates the total number of births to all women of reproductive age regardless of marital status. Rates based on a narrower age range (usually one-year or five-year age groups) are called age-specific fertility rates9 or age-specific birth rates9.
  1. In many expressions used in this and following paragraphs, birth rate is used synonymously with fertility rate.
  2. Marital fertility or legitimate fertility: the fertility of married persons (see 635-1).
  3. Non-marital fertility or illegitimate fertility: the fertility of unmarried persons.


Order-specific fertility rates1 relate births of a certain order to a number of women, to a number of marriages or to a number of births of the preceding order. Parity-specific fertility rates2 or parity-specific birth rates2 not only restrict the numerator to births of a given order, but also restrict the denominator to the women of the parity (611-6) at risk (134-2), e.g., second order births to one-parity women. Such rates are usually age-specific or duration-specific. In parity-specific birth probabilities3, the numerator consists of the number of births of order x + 1 occurring during a period, and the denominator consists of the number of women of parity x at the beginning of the same period.


When studying marital fertility1 it is possible to arrange the data by marriage cohorts (116-2) of the mothers, and marriage duration-specific fertility rates2 are often computed in preference to age-specific marital fertility rates3.


The term cohort fertility1 refers to the reproductive performance of particular birth or marriage cohorts (116-2). When the age-specific or marriage duration-specific fertility rates are summed from the cohort’s beginning of exposure to risk until some later date, we speak of cumulative fertility2: age-specific cumulative fertility3★ or marriage duration-specific cumulative fertility3★ when then ending date is that of a womans birthday or marriage (501-4), completed fertility4 or lifetime fertility4 is the cumulative fertility until the date when all members of the cohort have reached the end of the reproductive period. The sum of the products of the fertility rates of the cohort by the probability of survival of the women to successive ages could be called the cumulative net fertility5, age-specific net cumulative fertility6★ or marriage duration-specific net cumulative fertility6★ and net complete fertility7★ or net lifetime fertility7★ of the cohort.
  1. Before the end of the reproductive period, the terms incomplete fertility or fertility to date are employed to show that the cohort’s cumulative fertility may be expected to increase.


Censuses and surveys may provide information on fertility when they include questions on the number of children born to enumerated women or couples, either during the current marriage1, or overall. The mean number of children ever born per woman2 or average parity2 can be computed. The number of children per couple is sometimes called average family size3. It is also possible to calculate the mean number of births per marriage4. Special attention is paid to marriages of completed fertility5, those in which the wife had reached the end of the reproductive years before the marriage was dissolved. The final parity6 or completed parity6, i.e., the mean number of children per woman past the childbearing age, is not very different from completed fertility (636-4). The tabulation of final parity or completed fertility by number of children serves to compute series of parity progression ratios7; these are fractions whose denominator is the number of women with n children, and whose numerator is the number of women with n + 1 children. Special studies yield information on family formation8 and the family life cycle8. Among those, frequency of premarital conceptions9★, birth intervals (612-1) and the age at the birth of the last child10 for women of completed fertility are of particular interest.


Fertility histories1 or reproductive histories1 are accounts obtained for individual women of the important events in their reproductive lives, such as marriages, pregnancies, births, infant deaths, etc., and their dates. Fertility histories are often obtained retrospectively from surveys. Family forms1 are used in historical demography (102-1), where they are established for a married couple and its children by family reconstitution2 on the basis of vital records (211-3). A woman’s pregnancy history3 or pregnancy record3 contains detailed information about her pregnancies including the date when each began and ended, and the outcome of the pregnancy. Such detailed records on the timing of fertility have been used for various purposes. For example, they can provide information on natural fertility4, i.e., fertility in the absence of family limitation (624-4). They are also used to estimate fecundability5, the probability of conceiving per menstrual cycle (622-2). A distinction is made between natural fecundability6, in the absence of contraception, and residual fecundability7 in the opposite instance. The term effective fecundability8 designates a fecundability that is reckoned in terms of conceptions that result in live births only. The conception rate9 during the period of exposure to risk often estimated using the Pearl index10★ (613-1) is used to measure the effectiveness of contraception during periods of contraceptive use.
  1. Birth histories are usually limited to live births.
  2. When used alone, the word fecundability stands for natural fecundability.


A summary index of period fertility1, i.e., the fertility of a particular year or period, computed by the summation of the series of age-specific fertility rates constituting the fertility schedule2 and representing a synthetic measure of fertility3, is the total fertility rate4 or total fertility4. Other summary period indices can be obtained, such as the total legitimate fertility rate5, the summation of marriage duration-specific fertility rates, and the order-specific total fertility rate6, the summation of age-specific fertility rates order by order. The ratio of births to marriages7 is computed by relating the number of births of a given year, either to the marriages of the year, or to a weighted average of the marriages of the current and of the preceding years.
  1. Also, fertility distribution or fertility function.
  2. This is not a rate in the meaning of (133-4). Total fertility for a given year represents the number of children that would be bom per 1,000 women if they experienced no mortality and were subject to the age-specific fertility rates observed for that year. The period gross reproduction rate (see 711-4) which is derived by multiplying the total fertility rate by the proportion of female births, has often been used in the past, but the total fertility rate is preferred at present as the summary index of period fertility.
  3. Or total marital fertility. The term is also used to describe the sum of the age-specific marital fertility rates above age 20.


Where induced abortion (604-2) has been legalized, it is possible to compile statistics on legal abortions (604-4). The abortion rate1 is a measure of the frequency of abortion in a population during a given period, usually a year. Abortions may be related to the total population or to the number of women in the reproductive ages and may be specific for age, parity or any other characteristic. The abortion ratio2 is a measure of the frequency of abortions in relation to the number of live births (601-4) during the same period. The life-time abortion rate3 is the sum of age-specific abortion rates4★ and is a synthetic measure of abortion per woman or per 1000 women. These rates are the ratio of the number of abortions reported at each age to years lived by all women of the same age. If women can be classified according to their marital status, abortion rates by age and marital status5★ can be obtained. It is often also relevant to divide the number of abortions by the number of conceptions and so to calculate the probability that a pregnancy results in an abortion by age and marital status6★.

Chapter 7 • Population growth and replacement


The interaction of fertility, mortality and migration leads to a consideration of population growth1. A zero population growth10★ refers to a population of invariable size. It is convenient to regard population decline2 as negative growth3. A distinction may be drawn between a closed population4 in which there is no migration either inwards or outwards and whose growth depends entirely on the difference between births and deaths, and an open population5 in which there may be migration. The growth of an open population consists of the balance of migration6 or net migration6 and natural increase7, which is the excess of births over deaths8 or deficit of births over deaths9★ sometimes called the balance of births and deaths8. Any change in one variable affects the overall growth and structure of a population; in this context growth effects11★ and structural effects12★ are determined.


The ratio of total growth in a given period to the mean population of that period is called the growth rate1. Occasionally this rate is computed with the population at the beginning of the period rather than with the mean population as a denominator. When population increase over a period of more than one calendar year is studied, the mean annual rate of growth2 may be computed. In computing this rate it is sometimes assumed that the population is subjected to exponential growth3 during the period, and time is treated as a continuous variable. The size of an exponential population4 would grow as an exponential function of time. The exponential growth rate5 is equal to the instantaneous rate of growth5. The ratio of natural increase (701-7) to the average population during a period is called the crude rate of natural increase6 and is equal to the difference between the crude birth rate and the crude death rate. The vital index7 is the ratio of the number of births to the number of deaths during a period; this measure is no longer much used.
  1. When time is treated as a discrete variable, reference is made to geometric growth.
  2. This is occasionally called a Malthusian population, but the term is ambiguous in view of its sociological connotations (see 906-1).


It can be shown that when a closed population (701-4) is subjected to constant age-specific fertility and mortality rates (631-8; 412-1) for a sufficiently long period of time, its annual rate of increase will tend to become constant. This constant rate of increase is called the intrinsic rate of natural increase1, and a population which has reached this stage is called a stable population2. The proportion of persons in different age groups in such a population will be constant, i.e., the population will have a stable age distribution3. This stable age distribution is independent of the initial age distribution4 and depends only on the fertility and mortality rates that are kept constant. Human populations never reach exact stability in practice, as fertility and mortality rates constantly change, but the computation of a stable population as a model and of its intrinsic rates may provide an index of the growth potential5 of a set of age-specific fertility rates applied to a non stabilized age structure. Related to the growth potential, the moment of inertia of a population or demographic momentum11★ should be mentioned: it refers to the dynamics hidden in the age structure due to a delayed growth response caused by the biological fact that from the time of birth of a cohort (116-2) to the beginning of their period of fertility (620-1) a certain amount of time passes. A population may for this reason still grow, even though the birth rate drops long ago. The reverse case is also possible. The momentum is particularly altered in case of discontinuity in the evolution of births (during wars for example) and abrupt reversals of trends. A stable population in which the intrinsic rate of natural increase is zero is called a stationary population6. In such a population the numbers in a given age group are equal to the integral of the survivorship function (431-3) of the life tables taken between the upper and lower age limits of the group, multiplied by a factor of proportionality common to all age groups. A quasi-stable population7 is a formerly stable population with constant fertility and gradually changing mortality; characteristics of this type of population are similar to those of semi-stable populations8★ which are closed population with a constant age structure. A logistic population9 is a population growing in accordance with the logistic law10 of growth, i.e., a population in which the growth rate decreases as a linear function of the population already alive and which will tend asymptotically to an upper limit.
  1. The intrinsic rate, also called by its inventor Lotka, the true rate of natural increase, is equal to the difference between the intrinsic birth rate (or stable birth rate) and the intrinsic death rate (or stable death rate).
  2. Stable, adj. - stability, n. - stabilize, v.
    Stable population analysis uses the properties of stable population models to estimate various characteristics of real populations.
  3. Stationary, adj. - stationarity, n.


The study of reproduction1 (see § 116) or population replacement1 is concerned with the natural process through which a population replaces its numbers. The theory behind treats population as a renewable resource2 in the mathematical sense of the term. A distinction is drawn between gross reproduction3 or gross replacement3, where no account is taken of mortality before the end of the reproductive period (620-1), and net reproduction4 or net replacement4, in which this mortality is taken into account.
  1. Also reproductivity. For another sense of reproduction see 601-2.


In this study of replacement a number of indices, replacement rates1 or reproduction rates1 are used. Reproduction rates are generally female reproduction rates2 or maternal reproduction rates2. The female net reproduction rate3 is defined as the average number of live daughters that would be born to a hypothetical female birth cohort (116-2) which would be subjected to a set of current age-specific fertility (631-8) and mortality rates (401-2). A female gross reproduction rate4 is computed similarly on the assumption that mortality before the end of the reproductive age is zero. Male reproduction rates5 or paternal reproduction rates5 can be computed analogously using male births and a male birth cohort, and certain types of joint reproduction rates6 which take both sexes into account have been proposed. Where the experience of an actual cohort is used in the construction of reproduction rates, cohort reproduction rates7 or generation reproduction rates7 are obtained. The mortality and the fertility rates used in the construction of these rates will refer to different periods of time. Where statistics of fertility by age are not available, the so-called replacement index8 may be used. This ratio relates the quotient of the population of children of a given age (as a rule those 0-4 years) to the number of women of childbearing age in the actual population, to the corresponding quotient in the stationary population (703-6).


Other replacement indices are also computed. For instance, the net reproduction rate is sometimes split into a legitimate component1 and an illegitimate component2. Again, a nuptial reproduction rate3 has been computed, showing the number of legitimate daughters that will be born to a newly-born female if current rates of mortality, fertility, nuptiality and dissolution of marriage remain unchanged. Generally such rates are for females, but it would be possible to compute analogous rates for males.


The net reproduction rate (711-3) and the intrinsic rate of natural increase (703-1) are closely related to one another. The net reproduction rate measures the increase in the stable population (703-2) implied by the given age-specific fertility and mortality rates over a period equivalent to the mean length of a generation1 or the mean interval between successive generations1. This length of a female generation is equal to the mean age of mothers2 giving birth to live daughters, with current age-specific fertility and mortality rates. Period reproduction rates are current indices (cf. 152) which relate to hypothetical cohorts3 or synthetic cohorts3.
  1. The mean age of fertility, i.e., the mean age of the fertility schedule is only approximately equal to the mean length of a generation. The mean length of a male generation similarly is equal to the mean age of fathers at the birth of their children.


Population projections1 are calculations which show the future development of a population when certain assumptions are made about the future course of population change, usually with respect to fertility, mortality and migration. They are in general purely formal calculations, developing the implications of the assumptions that are made. A population forecast2 is a projection in which the assumptions are considered to yield a realistic picture of the probable future development of a population. Although the projection period3 is variable, short-term forecasts4 are the rule, as the margin of error to which forecasts are subject increases considerably as the length of the forecast’s period increases. The most frequently used method of projection is the component method5 or cohort-component method5 which takes the population distributed by age and sex at a base date6 and carries it forward in time, cohort by cohort, on the basis of separate allowances for fertility, mortality and migration. When matrix algebra is used for component projections, the method is sometimes called matrix method of projection7.
  1. Projections are also made in terms of educational, economic and social characteristics. Backward projections which might be more accurately called retrojections, use similar methods to trace the past evolution of the population.


Estimates of the population1 by size and composition at various dates in the past and present may be made by various methods, including many of the methods used for population projections (720-1). Demographic estimates2 include estimates of the population and of such characteristics as fertility (601-1), mortality (401-1), etc. The annual extrapolation of population5★ from the last census is carried out on the basis of the last census and vital statistics in subsequent years. Intercensal estimates3 relate to dates intermediate to two or more censuses (202-1), and take the results of these censuses into account. The error of closure4 is the difference between the size of a population enumerated at a new census and the population estimated for that census date on the basis of a previous census, the excess of births over deaths, and net migration (805-2) during the intercensal period. This difference represents the balance of errors in the data on births, deaths, net migration, and the coverage of the two censuses.
  1. Postcensal estimates take the results of a previous census into account, but not those of the next census.


A demographic model1 consists of a theoretical construct representing the evolution of a population (of individuals, couples, families, households, etc.) and its structure on the basis of its initial state and the effect of various demographic variables (such as fertility, fecundability, mortality, etc.). In a static model2, these variables remain constant; in a dynamic model3, they are allowed to change over time. A further distinction is made between deterministic models4 which assign functional relations between definite values of the variables, as if the studied population were infinitely large, and stochastic models5 or probabilistic models5 which consider the probability of various events occurring to individuals over the duration of the process under study. The model may be set out in mathematical formulas or take the form of a simulation6 where specific values of the variables are included in a system of relations. Macrosimulations7 may for example involve population projections made by the component method (720-5). In microsimulations8, events are made to occur randomly to individuals or groups over time according to sets of probabilities assigned to the variables in the model.
  1. The word is also used as an adjective in such expressions as model tables.

Chapter 8 • Spatial mobility


The study of spatial mobility1 or geographic mobility1 is concerned with the quantitative aspects of moves2 made by individuals in geographic space. The distinguishing characteristic of migration3 is that it involves a change in usual place of residence (310-6*) and implies movement across an administrative boundary. The administrative unit left by the migrant is the place of origin4 or place of departure4; the unit to which the migrant goes is the place of destination5 or place of arrival5. The concept of migration is often not applied to moves made by persons without a fixed place of residence, for example, nomads are excluded from the count of migrants in many countries. In practice it is sometimes difficult to distinguish between migration, which implies a relatively permanent change of residence, and temporary moves6, except on the basis of criteria of length of absence7 from the place of origin or duration of stay8 at the place of destination. In general, geographic mobility does not include short-term trips which involve no change of usual residence, even though such moves may deserve study because of their economic and social importance. Commuting9 involves the daily or weekly journey from place of residence to place of work or schooling; seasonal moves10 have a yearly periodicity. Transits11, which are moves across a territory to reach a destination, do not involve migration with respect to the territory crossed. Tourist traffic12 or vacationing12 also are not included in geographic mobility.
  1. Spatial mobility is distinguished from social mobility (920-4) and occupational mobility (921-3).
  2. Migration, n. - migrate, v. - migrant, n.: one who migrates, also used as adj. - migratory, adj.: pertaining to migration. The term migration refers to a process and cannot serve in English (in contrast to French) to describe a particular move; it is rarely used in the plural. Some authors view all residential mobility (803-6) as migration. For most, however, migratory moves involve the crossing of a boundary, and the administrative unit selected is called the migration defining area.
  3. The terms country of arrival and country of reception are appropriate when international migration is the subject of interest.
  4. Commute, v. - commuter, n.: one who regularly travels from his place of residence to his place of work. The expression journey to work is also used to describe this type of movement.
  5. Seasonal movement is more accurate than the frequently used term seasonal migration since these moves rarely involve a change of usual residence.


When migration is observed over time, it is convenient to compare the place of residence at a fixed past date1 or the place of last previous residence2 with the place of current residence3. An individual whose administrative unit of residence differs at the beginning and end of a certain interval is identified as a migrant4. Migrants may be classified as emigrants5 or out-migrants5 with respect to their place of origin and as immigrants6 or in-migrants6 with respect to their place of current residence. When a census or survey has included a question on previous place of residence2, the information generated concerns in fact the latest migration7 or latest change of residence7, whatever its date. A migrant is any individual who has had at least one prior residence in a different administrative unit from his or her current residence; such an individual can be considered to have migrated into8 the current residence, and migrated out9 of the previous one. A lifetime migrant11 is a person whose place of birth10 was in a different administrative unit from his or her current residence. In specific cases, migrants can be qualified as emigrants for political, religious or ethical reasons12★, or immigrants for political, religious or ethical reasons13★.
  1. Strictly speaking, under this concept a migrant must have been born before the beginning of the migration defining interval and must survive until the end. This definition is sometimes extended to include children born during the interval who are allocated to the place of residence of their mother at the beginning of the interval. The number of recorded migrants is not necessarily equal to the number of moves which occurred during the interval for these individuals, as any one may have moved several times in the interval, or even have returned to his previous place of residence by the time of the census or survey.
  2. Usually the place of birth is defined as the place of usual residence of the mother at the time of the birth even though custom or the location of medical facilities may have resulted in the birth occurring elsewhere.


The population of a sovereign country (305-3) may be involved in internal migration1 when both place of departure (801-4) and place of destination (801-5) are within the country, or in international migration2 which occurs across national boundaries. The term external migration3 is sometimes encountered in the latter sense. International migration is called immigration4 or emigration5 according to whether the country in question is the country of destination or the country of origin. When the country is divided into sub-areas, movement within the boundaries of each sub-area are local moves6 and constitute residential mobility6, while movement between sub-areas is called in-migration7 or out-migration8 depending on whether the sub-area considered is the place of destination or the place of origin for the migrants. A migration stream9 is a group of migrants having a common origin and destination. The larger stream between two sub-areas is called the dominant stream10 and the smaller the counterstream11.
  1. The definitions of migration in this paragraph can be extended to the migrants involved. The distinction between internal and international migration is not always precise when territories within a country are more or less autonomous.
  2. Simple commuting across a national border receives the name of border traffic, and should not be mistaken for international migration.
  3. Immigration, n. - immigrate, v. - immigrant, n. and adj.
  4. Emigration, n. - emigrate, v. - emigrant, n. and adj.


When an individual migrates several times during a certain period, his or her moves may be distinguished according to the order of migration1. The duration of residence2 or duration of stay2 refers either to the interval between the arrival in a place and the subsequent departure for another destination or to the interval since the most recent move. Return migration3 involves movement back either to the initial area, or to any previous place of residence. Repeat migration4 or chronic migration4 refers to a tendency to migrate several times over a relatively short time interval. Rural-urban migration5 sometimes takes the form of serial migration6, stage migration6 or step migration6, as migrants tend to move to large cities as a final place of destination by a series of shorter, intermediate migrations to cities or areas of successively larger size. The serial migrations7★ between a series of cities of different sizes is sometimes used when net migration of each city is positive and results from an excess of immigration from the rural sector and smaller cities over emigration to the larger cities.
  1. Individuals involved in return migration are called return migrants.
  2. When repeat migration involves moving to new areas, some authors talk of secondary migration and of secondary migrants, in contrast to primary migration which involves first order or primary migrants. This is a source of confusion, since these terms usually take the meaning of 806-4.


The contribution of migration (801-3) to overall population growth or population growth due to migration1★ (701-1) is due to net migration2, i.e., the difference between the number of arrivals3 and the number of departures4. Net migration can have a negative or a positive sign; net immigration5 or net in-migration5 is used when arrivals exceed departures, and net emigration6 or net out-migration6 when the opposite is true. The sum of arrivals and departures in a country can be used to measure the volume of migration7. A similar concept, applied to sub-areas of a country, is the migration turnover8. The net stream9 or net interchange9 of migration between two areas is defined as the difference between the stream (803-9) and the counterstream (803-11), whereas the gross interchange10 is the sum of stream and counterstream.
  1. This may also be called the balance of migration or the migration balance. Terms such as "net migrant" should be avoided, and phrases such as the net number of migrants should be preferred.


Spontaneous migration1, voluntary migration1 or free migration1 is the result of the initiative and free choice of the migrants. In the absence of concerted action, the movement is referred to as individual migration2. When entire families are moving together, the term family migration3 is sometimes encountered. Secondary migration4 or ancillary migration4 is induced by the movement of others, as when children follow the head of the family. An example of such migration is family reunification9★, which pertains to the migration of family members, including children, of the family head. The movement of workers or of members of the labor force in response to employment opportunities is referred to as labor migration5. Moves occurring as a result of marriage and when individuals retire from the labor force are sometimes referred to respectively as marriage migration6 or retirement migration7. Chain migration8★ or linked migration8★ refers to a pattern of migration to specific places of destination, where a prospective migrant has a relative (114-3*) or friend who has established a residence and is willing to provide information and support.
  1. Although the terms are sometimes used in a different sense (cf. 804-4*), a primary migrant is the person who makes the actual migration decision while a secondary migrant is an individual such as a young child whose migration is the result of another person’s decision.


Where groups of individuals or families decide to migrate together collective migration1 or group migration1 will result. Mass migration2 involves a very large number of migrants. The term exodus3 may be used for a sudden mass migration caused by some emergency or catastrophe.


Voluntary migration (806-1) contrasts with forced migration1, in which individuals are compelled by public authorities to move. Repatriation2 applies to forced return of individuals to their country of origin. Another example of forced migration is the expulsion3 from their places of abode either of individuals or of whole groups of people. The term evacuation4 is generally reserved for the movement of whole populations in order to safeguard them from some catastrophe, such as earthquakes, floods, operations of war or the like. A refugee5 has usually migrated on his own volition, though there may have been strong pressure on him to migrate because his continued stay in his country of origin may have exposed him to danger of persecution. A displaced person6 is a person who has been moved by a public authority from his place of origin. This move may have taken place as a result of large-scale displacement of population7 or population transfer7, or population exchange8.
  1. Repatriation, n. - repatriate, v.
  2. Expulsion, n. - expel, v - expellee, n., one who has been expelled. The term deportation is used for expulsion of an individual person from his country of residence because his continued residence is considered undesirable by the authorities. Deportation, n. - deport, v. - deportee, n.
  3. Evacuation, n. evacuate, v, - evacuee, n., a person who has been evacuated.


The process by which immigrants adjust themselves to conditions in the area of destination falls into several categories: naturalization (331-1), the acquisition of legal citizenship; absorption1 the entry into productive economic activity; assimilation3, integration into the social structure on terms of equality; and acculturation2 the adoption of the customs and values of the population in the place of destination.


When immigrants from a particular territory do not assimilate in their new country but retain the customs of their place of origin (801-3), they are called a colony1. When the receiving country is already inhabited, this raises problems of coexistence2 between different populations. These may be solved by the fusion3 of the populations, i.e. by the disappearance of recognizable differences, or by the integration4 of one of the populations into the other. Segregation5 exists in a territory where two or more populations live but remain separated by barriers imposed by custom or by the force of law.
  1. Colony, n. colonize, v., to found a colony, also used in the sense of settling a new territory - colonist, n., member of a colony.
  2. Coexistence, n.-coexist, v.
  3. Segregation, n. - segregate, v.
    In extreme cases, the conflict may result in genocide, i.e. an attempt by one population to exterminate the other. Exterminate, v. - extermination, n.


Migration policy1 is one aspect of population policy (105-2). Most countries through their immigration laws2, restrict the admittance of foreign nationals. These laws frequently provide for selective immigration3 of persons with certain specified characteristics. Some countries have established quota systems4 whereby the number of immigrants is fixed in relation to the national origin5. Measures designed to influence the redistribution of population6 within a country through internal migration (803-1) are usually more indirect in character.


Migration statistics1 are compiled to reveal the volume of migration, the direction of migratory movement and the characteristics of migrants. The accuracy with which each of these kinds of facts is ascertained depends upon the method of compilation, as most migration statistics consists of approximations and estimates rather than precise measurements. Direct measurement of migration2 requires a system of recording movements as they occur. The most complete migration statistics are developed from population registers in which all changes of residence are recorded. They allow measurement of internal and of international migration, but are more satisfactory for the former than for the latter. In countries where these population registers do not exist, a certain number of administrative record systems which do not cover the entire population can be used for particular purposes. Thus, voter registration records3, social security records4 tax-payers records5 or dwelling records6 may yield information on internal migration. In the case of overseas migration, statistics may be based on passenger lists7 or manifests7 of ships and aircraft. Counts of persons crossing a political frontier yield only very crude data; most of all in areas with much frontier traffic (803-2*) special steps must be taken to distinguish migrants from travellers8, who do not change their place of residence, and persons in transit 801-11). The number of visas9 or entry permits9 granted and the number of residence permits10 or labor permits11 issued may also be used as an indication of the migration of foreign nationals.
  1. Traveller, n. - travel, v. - travel, n.: the process of travelling.
  2. In certain countries residents who wish to travel abroad are required to obtain exit permits or exit visas, records of which may serve as a source of information on migratory movements.


Information collected in censuses and surveys allows the development of statistics on migrants1. Depending on the questions asked, these usually include statistics on in-migrants2, statistics on out-migrants2 and place-of-birth statistics3. This approach has limits for the study of international migration; emigrants cannot be studied, whereas immigrants are known, whatever their country of origin.


Where it is not possible to determine migration directly, indirect estimates of net migration may be obtained by the residual method1 or method of residues1 in which the change in population between two dates is compared with the change due to natural growth; the difference between the two figures is attributed to migration. The vital statistics method2 consists of computing the difference between total population change, as assessed from two censuses, and natural increase (701-7) during the intercensal period. The survival ratio method3 is commonly used to estimate net migration by age; it does not require actual death statistics. Survival ratios may be derived either from life tables or from the comparison of successive censuses, and they are applied to a sub-population in one census to give expected numbers by age at the time of the other census. A comparison between the observed and the expected population may be used to estimate the balance of migration by age for the subpopulation. When place-of-birth statistics4★ (813-3) by age and current residence are available in two consecutive censuses, it is possible to make indirect estimates of migration streams.
  1. The equation showing that the difference between total population change and natural increase is equal to migration has sometimes received the name of balancing equation. In order to use it for the estimation of net migration, one must assume that omissions (230-3) and multiple countings (230-5) are equal for both censuses.
  2. The major variants of this procedure are called the life table survival ratio method and the national census survival ratio method. In the forward survival ratio method, the population at the beginning of an intercensal period serves to estimate the expected population at the end of the period, and the procedure is reversed in the reverse survival ratio method; the average survival ratio method combines these two approaches.


The generic term migration rate1 refers to any rate which measures the relative frequency of migration within a population. Unless indicated otherwise these rates should be taken as annual migration rates2. They may be obtained as the ratio of the average annual number of movements during a certain period, to the average population of the period. An annual rate of net migration3 and an annual rate of total migration4 are calculated in a similar fashion by using the appropriate information on net and total migration. An index of migration effectiveness5 or effectiveness index5 is calculated as the ratio of net migration to total in- and out-migration. The range of the index is from zero, when arrivals and departures are equal in number, to one, when migration is entirely one way.
  1. Other denominators may serve to compute the rate, such as the population at the beginning or the end of the period, or the number of person-years lived by the population of the area.
  2. Also: Index of migration efficiency or efficiency index.


Proportions of migrants1 can be obtained by relating the number of migrants during a period to the population to which or from which they are migrating. When the proportion of out-migrants2 is obtained by dividing the number who reported moving out of the area by the population residing in the area at the beginning of the period and alive at the end, this index measures the probability of moving for the population at risk, and among other uses, it can be used in the preparation of population projections where migration is accounted for separately. But other populations are often used in practice as denominators to compute proportions of migrants. Similarly, the proportion of in-migrants3 is sometimes obtained by dividing the number of in-migrants in an area during a period, by the population of the area at the end of the period; but the denominator could also be the population at the beginning of the period, or the average of the beginning and end populations. The proportion of lifetime in-migrants4 can be derived from information on the place of birth, dividing the number of persons born out of the area by the enumerated population of the area. The proportion of lifetime out-migrants5 can be obtained by dividing the number of persons in a country living outside of their area of origin, either by the total number of persons born in that area, or by those among them who still live there. When such characteristics of the migrants as age (322-1), occupation (352-2) or level of education (342-1) are known, indices of migration differentials6 are used to contrast the migrants and the rest of the population of destination. The index is equal to the quantity 1 minus the ratio of the proportion of migrants in the population having the characteristic studied to the proportion of migrants in the whole population. The index of migration differentials is equal to zero when the population with the given characteristic has the same migration behavior as the rest of the population. The term selectivity of migration7 indicates that the comparison is between the in-migrants and the population from which they were drawn, at the area of origin (801-4). When comparing the characteristics of the in-migrants to those of the population at the place of arrival (801-5) the term differential migration8★ or migration difference8★ is sometimes used.
  1. For example, the selectivity of migration from Mexico was decreasing because differences in characteristics between migrants and nonmigrants fade over time; also the origins of Mexican immigrants was increasingly diverse because of the spread of Mexican migration networks in the USA.


Longitudinal migration analysis1 requires information on the successive moves of an individual over time, information which is normally available only from population registers (213-1) or retrospective surveys (203-8). Several refined measures of migration are available from this type of data, such as a first migration probability2, defined as the probability that a group of non-migrants3 aged x will be involved in migration for the first time before reaching age x + n . These probabilities can be used to calculate a non-migrant table4. The latter, when combined with a life table (432-3) will lead to a double decrement survivorship schedule of non-migrants5. Similarly, migration probabilities by order of move6 can be computed, as well as the proportion of migrants of a given order who have not gone on to make a subsequent move within a certain migration defining interval. The all orders migration rate7 is the ratio of moves of all orders in a year to the average population size of the cohort (117-2) over the year. The cumulation of these rates for a cohort up to a given date provides an estimate of the mean number of moves8 in the absence of mortality. A survivorship schedule can be combined with an age-specific all orders migration table9 to estimate the average number of remaining moves for an individual of a given age, given the prevailing mortality.


In studying migrants between two areas during a period, one commonly used measure is the index of migration intensity1, obtained by dividing the number of migrants from area A to area B by the product of the number of inhabitants in B at the end of the period, and the number of inhabitants of A at the beginning of the period who are still alive at the end. This index, divided by the ratio of the total number of migrants to the square of the population of the country, yields a migration preference index2. When the numerator is restricted to the net stream of migration, the resulting measure is called an index of net velocity3. The effectiveness of migration streams4 is measured by relating the absolute value of the net migration stream to the gross interchange (805-10).
  1. This index can be interpreted as the probability that two individuals alive at the end of the period selected randomly, one among those residing in area A at the beginning of the period, and the other among those residing in B at the end of the period, will be identical. The availability of data may impose various other denominators.


Migration models1 fall in two broad categories. The first relates migration streams (803-9) between two areas to social, economic or demographic variables. These variables are often classified as push factors2 when they characterize repulsion2 from the area of origin, as pull factors3 resulting in attraction3 to the area of destination, and as intervening obstacles4 between the two areas. The simplest of these models are gravity models5: the streams between the two areas are directly proportional to the size of their population, and inversely proportional to the distance6 between them, raised to a certain power. Other models consider that the streams are proportional to the opportunities in the area of destination, and inversely proportional to intervening opportunities7 between origin and destination. Models in the second broad category are stochastic models (730-5) and refer to individuals rather than to populations; they link the probability of migrating to a certain number of personal characteristics such as age or the previous history of migration.
  1. Or Pareto-type models.
  2. Distance can be measured in diverse ways: a straight line, the route, the number of intervening areas, etc.

Chapter 9 • Economic and social aspects of demography


A part of population theory (105-1) is concerned with the social and economic determinants and consequences of population trends. The theoretical treatment of population was largely centered in the past on the relation between total population and resources1, i.e., the means available to maintain the population, or production2, the creation of goods and services. More recently, the emphasis has shifted to the interrelations between population growth (701-1) and its components, and economic growth (903-1), particularly with respect to consumption3, saving4, investment5 and labor market6★.


Consideration of the relations between population size and resources leads to the concepts of overpopulation1 and underpopulation2. These terms are defined only at a given fixed level of development3. When neither a larger nor a smaller population would yield advantages, there is said to be an optimum population4, sometimes briefly called an optimum4. The advantages yielded may be economic in character and in that case it is an economic optimum5. The discussion of economic optima generally proceeds in terms of economic welfare but, as this is difficult to ascertain empirically, the level of living6 or standard of living6 is sometimes substituted. This is approximated by the real national income per capita7 i.e., the total amount of goods and services produced in a particular period (or its equivalent in money income adjusted for variation in purchasing power) divided by the total population during the period.
  1. Overpopulation, n. - overpopulated, adj.
  2. Underpopulation, n. - underpopulated, adj.
  3. Some writers have used the concept of a power optimum and a social optimum as well as of an economic optimum.
  4. The expression "standard of living" is restricted by some economists to mean an accepted goal or recognized set of needs, as constrasted with the level of living actually attained. Others use these terms interchangeably.
  5. Other measures such as the gross national product per capita, are also used. "Per capita", although grammatically incorrect, is used in place of the expression "per head".


Economists have emphasized the dynamic relations between economic growth1 or economic development1 and rates of population growth and changes in population structure; they are less interested today in the static concept of an optimum size, than in the dynamic concept of the optimum rate of growth2 of population, i.e., the rate of growth which will be consistent with the maximum rate of increase of the level of living. These relations are of particular concern in countries with a low level of living, which have come to be called less developed countries3 or developing countries3.
  1. Also: underdeveloped countries or low-income countries. They are commonly contrasted with the developed countries, or more developed countries.


The maximum population1 of a territory, sometimes called its carrying capacity1, is generally understood in an absolute sense to mean the largest number of persons that could be sustained under specified conditions; but is sometimes used to denote the largest number that could be supported at an assumed standard of living. Conversely, the minimum population2 is generally taken to be the smallest number of persons in an area which is consistent with group survival3.


The term population pressure1 is linked to concepts relating the size of the population and the resources (901-1) available. To say that this pressure is strong or weak in a certain area is to suggest that the population of the area is near or far from the maximum consistent with the resources which are available. According to Malthusian population theory2, so called after its originator, Thomas Malthus, there will inevitably be pressure of population on the means of subsistence3. Any change in the volume of available means of subsistence would generate population growth (701-1) until population equilibrium4 would again be attained when the level of living had reached a subsistence level5, i.e., a level just sufficient to maintain life. The equilibrium would be maintained by the elimination of any surplus population10★ either through positive checks6, sometimes known as Malthusian checks6 (famine, pestilence and war), or through the preventive check7 of moral restraint8 consisting of postponement of marriage9, coupled with abstinence from sexual relations before marriage.
  1. and 7. The terms positive check and preventive check in English are generally used only with reference to the doctrines of Malthus.


Although the term Malthusianism1 originally refers to the theories of Malthus, it is often used today to denote the doctrine that a check in the rate of population growth is desirable. Neo-Malthusianism2, whilst accepting the desirability of checking population growth, advocates that such restriction should be achieved through the use of birth control methods (627-3).
  1. Malthusianism, n. - Malthusian, adj.: conforming to the doctrines of Malthus. The terms are sometimes used mistakenly to refer to the advocacy of family planning programs to solve economic problems.


The process of transition from a situation in which both fertility and mortality were relatively high to one in which they are relatively low which has been observed in many countries, is called the demographic transition1 or population transition1. In the process of moving from a pre-transitional stage2 to a post-transitional stage3, there is typically a lag between the declines of mortality and fertility, so that a stage of transitional growth4 of population results. Economists have studied changes in productivity5, i.e., production per member of the labor force, or per head of the population, associated with this transitional period.
  1. Sometimes called the vital revolution. A further distinction is made between the fertility transition and the mortality transition. The theory of the demographic transition associates historical changes in vital rates with socio-economic transformations attending the process of industrialization and urbanization.


In eugenics1, a discipline which seeks to improve the quality of the population, attention is directed primarily to the role of heredity2, the transmission of hereditary characteristics3, such as the color of the eyes, from generation to generation. Acquired characteristics4 are not so transmitted. A lethal characteristic5 generally brings about the early death of the foetus.
  1. Eugenics, n. - eugenic, adj. - eugenist, n.: a specialist in eugenics.
  2. Heredity, n. - hereditary, adj.


The transmission of hereditary characteristics operates through genes1 which are transmitted to children by their parents. Genetics2 is the science concerned with the transmission and effects of hereditary factors. The genes are carried by chromosomes3 which are long filaments of DNA (deoxyribonucleic acid) located in the cell’s nucleus. The position of a gene on a chromosome is called its locus4. Genes occupying the same locus affect the same characteristic, although they do so in various ways which correspond to various alleles5 of the gene in this locus. The new cell formed by the union of two sexual cells or gametes6 during the process of conception (602-1) is called a zygote7.
  1. All of the genes carried by an individual are collectively called his or her genetic endowment.
  2. Genetics, n. - genetic, adj. - geneticist, n.: a specialist in genetics.


The set of two genes of an individual at the same locus is called a genotype1; the genotype is said to be homozygous2 if the alleles are identical at a given locus; it is said to be heterozygous3 in the opposite case. The phenotype4 consists in the observable characteristics as determined by the genotype and the environment. If an heterozygous individual (AA’) cannot be distinguished from an homozygous individual (AA), the allele A is said to be dominant5 over allele A’, and A’ is said to be recessive6. Genes are subject to sudden and apparently random changes, called mutations7. Panmixia8 or random mating8 insures uniform distribution of genes within populations.
  1. Mutation, n. - mutant, adj. or n.


A distinction is frequently made in eugenic policy between positive eugenics1, aimed at increasing the number of persons believed to have desirable characteristics, and negative eugenics2 aimed at restricting the reproduction of persons expected to transmit undesirable characteristics or hereditary defects3. Much attention has been given to the discussion of eugenic sterilization4, i.e., the sterilization of persons likely to transmit undesirable characteristics to their descendants. Objections to this measure have been raised on moral grounds and also because of its relatively low efficiency in reducing the frequency of recessive genes (912-6). Among the measures proposed, pre-marital examination5 may be mentioned; this is designed to give couples intending to marry information about the probable quality of their offspring, so that prospective partners to dysgenic marriages6, i.e., those likely to produce defectives, may be warned.


The probability that an individual of reproductive age will have a given number of offspring who also attain reproductive age may depend on his genotype (912-1). This differential reproduction is called selection1. The selective value2 or fitness value2 of a genotype is the relative number of children of individuals with the genotype who survive to reproductive age. The mean selective value3 or fitness3 of a population is equal to the average of the selective values for the genotypes of its members. The genetic load4 of the population is the relative decline in the mean value of fitness resulting from the presence of different genotypes with varying fitness values. Random fluctuation of the frequency with which a specific gene is found in different generations of a population is called the genetic drift5. The gene structure6 of a population refers to the distribution of the frequencies of different alleles (911-5) on a given locus (911-4) within the members of the population. The genotypic structure7 of a population refers to the distribution of different genotypes on the same locus.


In the case of an inbred individual, i.e., an individual whose parents have a common ancestor, two genes are said to be identical genes1 by descent, if both were carried by the same ancestor and are on the same locus. The probability that an individual chosen at random in a population carries two genes identical by descent is the coefficient of inbreeding2 of the population. The coefficient of kinship3 of a population is the probability that two individuals chosen at random in that population carry genes identical by descent on the same locus.


In many studies, the population is divided into a number of social status groups1 or into socioeconomic groups1 according to occupation, income, education or similar indices of economic status. The term social class2 has a sociological connotation which is only approximated by the type of grouping generally used in demographic work. The division of society into a number of such groups is called social stratification3. Movement between different social status groups is called social mobility4; a distinction is made between upward mobility5 and downward mobility6 in the social hierarchy. The mobility of children with respect to their parents’ social class is called inter-generational social mobility7.
  1. A caste is a closed social group in which social status and position in the social hierarchy are ascribed.
  2. Social mobility by an individual in his or her own lifetime is called intra-generational social mobility.


Labor mobility1 is the general term that covers not only an individual’s changes of occupation2 under the name of occupational mobility3 but also job mobility4, or changes of employer, and industrial mobility5, or changes of industry.


Interest in the problems of aged persons (324-8) and aging (326-3) has given rise to a special branch of studies called gerontology1 including the special branch of medicine called geriatrics2.
  1. Gerontology, n. - gerontological, adj. - gerontologist, n.: a specialist in gerontology.
  2. Geriatrics, n, - geriatric, adj. - geriatrician, n.: a specialist in geriatrics.


A population policy (105-2) is a series of measures taken by public authorities to influence the trend of population change, or principles offered as a basis for such measures. A distinction is made between populationist1 policies designed to increase the population, to accelerate its rate of growth or to check actual or incipient population decline or depopulation2, and population control3 policies for the purpose of checking population growth or reducing the rate of population increase. Among the former, pronatalist4 policies, which attempt to increase the birth rate (332-1), are particularly important. In contrast to pronatalist policies, there are antinatalist5 policies, which are designed to reduce the frequency of births. Population policy may also include a component of population redistribution6 policy designed to influence the territorial distribution of population, as well as a component of migration policy7★. Health policy8★, which aims to reduce morbidity (420-1) and mortality (401-1), is an other component of population policy.
  1. Also called Malthusian policies. See 906-1.


In many countries allowances1, benefits1 or grants2 are given to the parents of children. In general an allowance is a sum of money which is paid periodically, whereas a grant is paid on a single occasion only. Family allowance3 or children’s allowance3 denotes a sum of money paid regularly to parents with a specified number of children. In many fiscal systems, tax rebates4 are granted in respect of dependent children. Other monetary benefits paid in some countries include maternity grants5 or birth grants5 which are paid upon the birth of a child, pre-natal allowances6 paid to expectant mothers during pregnancy, and on occasion marriage loans7 granted to newly-married couples in order to assist them in setting up a household.


Many other public measures, such as housing programs or measures in the field of public health1, may have an impact on demographic phenomena. The provision of services for pregnant women such as pre-natal clinics2 and for parturient (603-4*) women may help in reducing late foetal, infant and maternal mortality (cf. 410, 411, 413, and 424-5). Services which are primarily designed to help the mother are called maternity services3; those meant to assist the child are infant welfare services4 or child welfare services4.


Population programs1 designed to reduce fertility in developing countries have included family-planning education2 and family-planning services3, either alone or in association with health programs4 and social welfare programs5, particularly maternal and child health programs6 designed to reduce mortality. Some countries have attempted to resort to incentives7 and disincentives8 of various kinds to elicit the motivation to use family limitation; social pressures9 and legal sanctions10 against disapproved fertility behavior are also encountered.The English term "Population Education11★" is used untranslated in some countries, especially Germany. In this specific context, it refers to the dissemination of information (in schools and other contexts) about the impact of individual reproductive behavior on broader society.