Census
Census
A census of the population—that is, a counting of the people within the boundaries of a country— has become indispensable to any modern government. How many people are there? What are their basic socioeconomic characteristics? Where do they live, and how are they affected by the processes of social and biological change? These questions arise daily in the governments of all industrially developed countries, not to mention the governments of those that are still developing.
Censuses have come to include many topics other than population. Censuses of manufactures, agriculture, mineral industries, housing, and business establishments are taken by many countries, often independently of the census of population.
The following discussion is concerned primarily with censuses of population, but many of the comments—especially the comments on methods, tabulation, and quality of results—apply with equal force to other kinds of censuses.
Some early censuses. Counting the people, or some portion of them, is a practice that is probably as old as government itself. No one knows which ruler first enumerated the men for military purposes, or drew up a list of households with a view to taxing them. Figures obtained from censuses have long served as items of political propaganda, particularly in order to justify territorial expansion.
Population counts were reported in ancient Japan and were taken by the ancient Egyptians, Greeks, Hebrews, Persians, and Romans. Many of these early censuses appear to have covered only part of the population, often the men of military age, and the results were generally treated as state secrets. In Europe censuses on a city-wide basis or, as in Switzerland, on a canton-wide basis, were reported in the fifteenth and sixteenth centuries. A 1449 census of Nuremberg presumably was taken to determine the needed food supplies when a siege was threatened. The city of Madras in India reportedly took a census in 1687.
Various censuses have been claimed as the first held in modern times with purposes and methods resembling those of today. Among these are a census in New France (the early possessions of France in North America) taken at intervals between 1665 and 1754 and a census in Sweden in 1749. Census taking began early in the North American and South American colonies. The British Board of Trade ordered 27 censuses in the North American colonies between 1635 and 1776, and censuses were taken by these former colonies between independence in 1776 and the establishment of the United States.
The oldest continuous periodic census is that of the United States, which has been conducted every ten years since 1790. The census of the United Kingdom dates back to 1801, and a census has been taken there every ten years except in 1941, during World War II.
If one were to define a modern census as one in which information is collected separately about each individual instead of each household, then the beginning of modern censuses would have to be dated about the middle of the nineteenth century. Censuses along these lines were taken in Brussels in 1842, in all Belgium in 1846, in Boston in 1845, and in the entire United States in 1850. This is the procedure that is now generally in use.
International activities. Toward the end of the nineteenth century, the International Statistical Institute recommended international publication of the results of all censuses. Around the turn of the century the institute repeated its recommendation, pointing out that the results of some 68 different censuses were available, covering about 43 per cent of the world’s population. The institute had already adopted, in 1897, a set of rules for conducting censuses and presenting their results, while the whole topic had been discussed by the International Demographic Congress as early as 1878.
One of the early proposals considered by the United Nations was that it develop plans for a 1950 world census of population. Although it found that conditions were not ripe for such an effort, the United Nations took steps to foster census taking and made recommendations to improve the comparability of results. The Inter American Statistical Institute meantime had undertaken a program for the 1950 Census of the Americas, and 18 of the 21 countries in the Americas took censuses between 1945 and 1954. Throughout the world at least 150 areas took censuses in this period, collecting individual data on more than 2 billion people. For the decade centered on 1960, the number of censuses was about 180, including 2.2 billion people.
The use of censuses. The reasons for taking a census vary with the needs of the countries involved. The current concern with social and economic development is one of the prime reasons. Much information is needed in order to institute programs that will improve health, literacy, education, income, levels of living, supplies of food and other consumer goods, agricultural production, and industrial output. Census data are also collected in order to determine the representativeness of legislative bodies, the number of persons eligible to vote, and the areas or groups that have a claim to benefits deriving from the state.
The census provides a basis for much demographic, economic, and social research. It makes possible the identification and description of such groups as the labor force, economically dependent persons, recent migrants to cities, rural and urban populations, racial or religious minorities, refugees, scientific and technical workers, and others. Comparisons of successive censuses show changes in the numbers, characteristics, and location of the population. The census returns are also used as a frame from which samples are selected for subsequent inquiries.
The modern census
The United Nations (1958, p. 4) gives the following definition of a modern population census: “A census of population may be defined as the total process of collecting, compiling and publishing demographic, economic and social data pertaining, at a specified time or times, to all persons in a country or delimited territory.”
It also listed six essential features of a census, as follows. (1) A census must have national sponsorship. Only a national government can provide the necessary resources and enact suitable legislation, although provincial and local governments may share a part of the responsibility and sometimes a part of the cost. (2) A census must cover a precisely defined territory, boundary changes that affect comparisons between successive censuses should be clearly and explicitly stated. (3) All persons in the scope of the census must be included without duplication or omission. (4) The people must be counted as of a fixed time. Persons born after the census date are to be excluded, and persons who die after the census date are to be included. Some information, such as that relating to labor force participation or migration, may relate not to the census date but to another period, which must be clearly defined. (5) Census data must be obtained separately for each individual. This does not preclude making some entries for the entire household—and in exceptional circumstances summarized information for a group of persons may be acceptable—but the objective of a modern census, insofar as possible, is to collect data separately for each individual. (6) The data from a census must be published. Although at one time census reports were treated as state secrets, it is now recognized that a census is not complete until the data are compiled and published.
What is included. The content of a census, no less than its purpose, is determined by the country’s needs at the time. Questions of high importance in one country may be of relatively little importance in another, and questions of great significance at one time may be of little significance later. Every national census has changed over the years. Conditions in the country, alternative sources of information, and the ability of the census organization to provide the proposed information chiefly determine the census content.
The United Nations has approved a set of recommendations for national population censuses that includes the following list of question topics: location at time of census and/or place of usual residence, relation to head of household or family, sex, age, marital status, place of birth, citizenship, whether economically active or not, occupation, industry, status (as employer, employee, etc.), language, ethnic or nationality characteristics, literacy, level of education, school attendance, and the number of children born to each woman (Principles and Recommendations … 1958). For countries that could not include all items in the list, the following were suggested as a minimum: sex, age, marital status, and some indication of economic activity. Each item listed, of course, requires specific definition. Some items, such as marital status, type of economic activity, or level of education, apply to only part of the population.
Collection of data. Discussions of census methods generally distinguish between a count based on the actual location of the population on the census date and one which relates each person to the place of which he is a resident. Frequently residence is interpreted as the place where the person usually lives, although “usual residence” has no statutory meaning. On either basis national totals are usually about equal; community totals, however, may differ substantially.
To facilitate international comparison, the United Nations (Principles and Recommendations … 1958) has suggested the adoption of an “international conventional total.” This would include all persons present in the country on the census date except foreign military, naval, and diplomatic personnel: it would also include the country’s own military, naval and diplomatic personnel and their families located abroad, and merchant seamen normally resident in the country but at sea on the census date. The same document recommends that counts or estimates of the following groups should be given where feasible: indigenous inhabitants and nomadic tribes, civilian national residents temporarily abroad on the census date, and civilian aliens temporarily in the country on the census date. This is because whether or not these groups are included in a national census is usually determined by the laws and needs of each country; thus detailed comparisons between national totals can be made only if separate enumerations of these groups are made available.
Customarily two basic methods of collecting census data are recognized—direct enumeration and self-enumeration. Under the direct enumeration system, an enumerator collects information directly from the individual concerned, the head of the household, or some other member of the household who may be authorized to report for him. Under the self-enumeration system, the questionnaire is given to the individual, or the head of the household, who is expected to enter the required information and return the questionnaire to the census office. In self-enumeration the enumerator often delivers and collects the questionnaire. He may assist persons in making the entries, and he is responsible for assuring the accuracy and completeness of the completed questionnaires.
In a few countries the people are required to present themselves at a designated place to be enumerated. In a few others the population is immobilized on the census date, and no one is permitted on the streets unless he has been enumerated. In the great majority of cases the census enumerator seeks out the potential respondents and delivers questionnaires to them or asks them directly for the required information.
Census legislation normally provides that respondents must give full and correct information. This information must be given confidential treatment by all census employees. For persons who do not wish to have other members of their households or local officials see the information about themselves, census offices have provided special forms on which the person can insert the information and send it directly to the local, regional, or national office.
Population registers and lists of households, where available, are often used to help make the census complete. In some censuses the first step in the field work is to establish a list of housing units. The numbers assigned to these units are then used to control the completeness of the enumeration.
The questionnaire must be designed to permit ready entry of the required information and also be adapted to the tabulation procedure. In self-enumeration there is customarily a separate form for each household, with space for entering information for each household member. When information is collected directly by enumerators they may carry a separate form for each household or a form on which information is recorded for a number of households. Sometimes a separate document is used for each person.
Some countries have a long-established tradition of taking a census once every ten years, a few countries require one every five years, but most countries take a census when it is needed and do not have a fixed date. In a few unusual situations censuses have been taken more often than once in five years. Whether by law or by custom, the ten-year term appears to be most common.
In an increasing number of countries a pilot census is taken before the full census to test the inquiries, the procedures, the development of the field organization, and sometimes the tabulation program.
Use of sampling. Sampling has been extensively used in connection with censuses, although a census in principle requires that information be collected for each person. The term “sample census,” which is sometimes used, is a misnomer; a collection of information relating to only a specified part of a population should be termed a sample survey. In some censuses a part of the questions are asked of only a sample of all individuals; in this way more information can be collected without a comparable increase in respondent burden or tabulation work load. Many countries base some tabulations on a sample of the population instead of the total to provide preliminary totals for early release or to reduce the cost of some final tabulations. Sampling has been used to control the quality of the work at several stages of the processing of the data. In some countries a sample has been selected for a pretest and the resulting data have been used to validate the processing operations.
Tabulation of results. To be useful, individual census returns must be converted to statistical summaries. Tabulation methods vary from simple hand counts to processing on high-speed electronic computers. Processing may be done in the field, in provincial offices, or at the central office.
Questionnaires as received from the enumerators must be reviewed to locate incomplete or inconsistent entries. Procedures have been developed for correcting such errors by utilizing other information on the questionnaires or by using probability distributions based on data from other sources. In many instances the entries on the schedule must be converted to a numerical or other suitable code to facilitate counting and grouping into appropriate categories.
The most common procedure for grouping the entries is to punch cards and tabulate them by mechanical means. More recently, electronic computers have been adapted to this work, and devices have been developed to transfer the original questionnaire entries directly to the magnetic tape used in these computers. The capacity and speed of the computers have led to important advances in the amount of material tabulated and in the timeliness of the publications.
Completeness and accuracy. In view of the many public and private uses for census data, there is increasing concern with the quality of the results in terms both of completeness of coverage and accuracy of returns.
Completeness of coverage has received major attention. Unless special precautions are taken, some individuals may not be counted and some areas may not be enumerated. Undercounts of the population are more frequent than overcounts, although a few zealous census officials have been known to overcount the population of an area. Omission of individuals may arise from incomplete enumeration of a household or an area. Underenumeration has been particularly marked in the case of infants and young adults who are highly mobile or who lack firm occupational attachments. In cultures where men are considered more valuable than women, the number of women may be understated. In a few instances a fear that the census may be used for military conscription has led to some omission of men or to misreporting them as women.
Reporting residence may present problems. Some persons, such as migratory workers, have no usual place of residence. Others, such as college students, members of the armed forces, and persons engaged in long-distance transportation, may live away from their families for short or extended periods. Unless precise instructions are given for reporting these persons, they may be counted twice or not at all.
Age is often misreported either because people see some advantage in giving the wrong age or because they do not know their correct age. In many countries births are not recorded, and age is not precisely known. Some reasons for misreporting are that a person believes that despite pledges of confidentialness, the data will be used to his disadvantage; a parent believes that overstating a young child’s age may gain him entrance to school or that overstating an older child’s age may free him from compulsory school attendance; an older person may overstate his age to get social security benefits or to acquire the higher status sometimes accorded to the very old. Often people report a number ending in zero or five—even when asked for year of birth.
Nationality, citizenship, and mother tongue are particularly subject to misstatement when the correct answer may be considered detrimental in the context of the political situation of the group controlling the area.
Improvement of quality. Public confidence in the census greatly affects accuracy of returns. Public confidence can often be increased through an informational campaign, which explains that the data about any individual cannot be used to his detriment. Police officers, who are used as enumerators in some countries because of their availability and authority, are specifically excluded in others because they may give the impression that the information is not collected solely for statistical purposes.
To improve the quality of results, research has been devoted to reliability of response, role of enumerators, question wording, and attitudes of respondents in different situations. Increased attention is also being given to training the temporary field forces in census methods and concepts and in training the office staff in principles of editing and coding.
The quality of census statistics can often be determined by analyzing them after the complete census tabulations have been published. Formerly this work was performed mainly by scholars or by census officials willing to do scholarly work on their own time; but modern census offices increasingly are undertaking such analysis as part of their regular work. Checks are made for internal consistency of the census, for consistency with previous censuses, and also with other statistics, including estimates, that are entirely independent of the census. Both underenumeration and overenumeration of an age group can be determined by comparing the census results with the comparable age cohort for the previous census, adjusted for deaths and migration [seeCohort analysis]. Inaccuracies in age reporting that result from the preference of respondents for certain ages can be identified by internal analysis of the data. Sometimes the accuracy of census information for individuals is tested by comparison with information given for these same individuals in administrative records. Sample surveys may be taken to check on completeness of coverage and accuracy of census returns.
These evaluations aid in increasing the accuracy of future censuses, but they also provide users of the statistics with information about the reliability of the data. Although there has been some hesitation about revealing errors in the census, there is a growing recognition that full and frank disclosure leads not only to improvement in future censuses but also to increased public confidence.
Conrad Taeuber
[See alsoFertility; Government statistics; Mortality; Population; Vital statistics.]
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