A national census of population is "the total process of collecting, compiling, evaluating, analysing and publishing or otherwise disseminating demographic, economic, and social data pertaining, at a specified time, to all persons in a country" (United Nations 1988, p. 3). The United Nations encourages its members to take regular censuses and provides technical assistance. It also publishes an annual demographic yearbook and maintains a web site with selected census data and other population information for most countries.

A nation may conduct censuses on other subjects such as housing, business firms, agriculture, and local governments. Because of the close link between families and housing units, censuses of population and housing are usually combined.

The actual enumeration for a national population census is usually spread over a period of weeks or months, but an attempt is made to record circumstances as of a designated census day (April 1 for the 2000 U.S. census...