census

A census is an official count of a population, typically accompanied by basic information about individuals and households. It is conducted by a government at regular intervals to determine the size, distribution, and characteristics of a population for governance, planning, and research. Common data collected include age, sex, ethnicity, occupation, education, household composition, and housing tenure.

Historically, censuses have roots in ancient administrations and evolved into modern nationwide operations during the 18th–19th centuries. The modern census emerged in Europe and North America, with many countries adopting regular decennial censuses. Some jurisdictions also collect more frequent data through annual surveys or integrated population registers.

A census typically aims to count every person, as opposed to sample surveys, and may be conducted as a population census, a housing census, or a combined exercise. Counting methods vary, including self-response questionnaires, interviewer-administered forms, and increasingly online submission. Some countries use de jure counting (usual residence) while others use de facto counting (where the person is found). Data collected can cover demographic, social, economic, and housing characteristics; the exact design depends on national needs and laws.

Uses of census data include apportionment of legislative seats, redistricting, allocation of public funds, and planning for schools, healthcare, transportation, and social services. Privacy protections and data confidentiality are central, with restrictions on disclosure and limits on how data may be linked to individuals.

Challenges include undercounting, nonresponse, data quality, costs, and political or social sensitivities. The rise of online collection and the use of administrative records are changing census design and implementation.