Census
A census is the official process of completely enumerating a population within a defined territory to collect demographic, economic, and housing data, typically conducted at least every ten years under government sponsorship.[1][2] This enumeration provides empirical baseline data for governmental planning, enabling the allocation of resources, apportionment of legislative seats, and formulation of policies grounded in actual population distributions rather than estimates.[3][4] Originating in ancient civilizations, the earliest known census dates to approximately 3800 BCE in Babylon, with the oldest surviving records from China's Han Dynasty around 2 CE, which counted households, population, and land for taxation and military purposes.[5] Roman censuses, conducted every five years from 406 BCE, similarly served administrative functions like citizen registration and resource assessment.[5] In the modern era, the United States established the decennial census in 1790, as required by the Constitution to determine congressional representation and direct taxes, marking a shift toward systematic, nationwide data collection that influenced global practices.[6] Censuses have evolved to include detailed variables such as age, sex, race, ethnicity, income, education, and housing conditions, facilitating causal analysis of social and economic trends.[7] However, achieving universal coverage remains challenging due to factors like population mobility, privacy concerns, and non-response, resulting in differential undercounts—such as those observed in the 2020 U.S. Census for certain racial and ethnic groups, including Hispanics (4.99% net undercount) and Blacks (3.30% net undercount)—while overall national coverage showed no significant net error.[8][9] These inaccuracies can skew apportionment and funding distributions, underscoring the tension between comprehensive enumeration ideals and practical execution limitations.[10] Despite such issues, censuses remain the most reliable source of granular, territory-wide population data, underpinning evidence-based governance over speculative approximations.[4]