census, periodic official count of the number of persons and their condition and of the resources of a country. In ancient times, among the Jews and Romans, such enumeration was mainly for taxation and conscription purposes. The introduction of the modern census—a periodic and thorough statistical review—began in the 17th cent. The first efforts to count people in areas larger than cities at regular periods were in French Canada (1665), Sweden (1749), the Italian states (1770), and the United States (1790). The first British census was taken in 1801. The Belgian census of 1846, directed by Adolphe Quetelet, was the most influential in its time because it introduced a careful analysis and critical evaluation of the data compiled. Most industrialized countries now take a census every 5 to 10 years.

Scientific census-taking in the United States began with the decennial census of 1850, when the scope and methods were greatly improved by making the individual the unit of study. In 1902 the Bureau of the Census was established in the Dept. of the Interior; the following year it was transferred to the Dept. of Commerce and Labor and remained in the Dept. of Commerce when the Dept. of Labor was separated (1913). In addition to being a vital source of statistical data about the nation, information from the U.S. census is also used to allocate federal resources.

The government was criticized and also sued for undercounting the homeless and minorities in the 1990 census. In 1996 the Supreme Court ruled that the decision to adjust the count is left to the discretion of the secretary of commerce. The government proposed remedying the problem of undercounting through the use of statistical adjustments to the 2000 census, but the Supreme Court ruled (1998) against the plan, and the traditional head-count method prevailed. In 2001 the government again decided to use unadjusted census figures. About 3.3 million people, largely minorities, were estimated to have been missed by the 2000 census; a smaller number were thought to have been counted twice. Unadjusted census figures are generally believed to favor Republicans in the drawing of districts for the House of Representatives.

Census of Marine Life, an international program to assess and explain the diversity, distribution, and abundance of living organisms in the oceans. A 10-year project involving scientists in more than 70 nations, the census began in 2001 and is directed by an international scientific steering committee, subcommittees, and national and regional committees. In addition to coordinating field surveys, which have identifed previously unknown species, the census is producing the Ocean Biogeographic Information System to manage the database that results. Historical research is also being undertaken so as to provide an understanding of the past diversity and distribution of marine species. The secretariat for the project is at the Consortium for Oceanographic Research and Education, Washington, D.C.

Enumeration of people, houses, firms, or other important items in a country or region at a particular time. The first U.S. population census was taken in 1790 to establish a basis for representation in Congress. Censuses were taken in England, France, and Canada in 1801, 1836, and 1871, respectively. China was the last major country to report a census, in 1953. Census information is obtained by using a fixed questionnaire covering such topics as place of residence, sex, age, marital status, occupation, citizenship, language, ethnicity, religious affiliation, and education. From the responses demographers derive data on population distribution, household and family composition, internal migration, labor-force participation, and other topics. Seealso demography.

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