Glossary

American Community Survey (ACS)

An ongoing U.S. Census Bureau survey providing detailed annual demographic, social, and economic data.

Also called: ACS

The American Community Survey is a continuous survey run by the U.S. Census Bureau that collects detailed demographic, social, economic, and housing data, income, education, commute times, language spoken at home, and more, from a sample of households every year. It replaced the long-form questionnaire that used to be part of the decennial census.

Because it samples rather than counts everyone, the Bureau publishes estimates with margins of error, and it releases both 1-year estimates, which cover larger areas and are more current, and 5-year estimates, which reach down to small geographies such as an individual census tract by pooling data across five years to get enough sample for reliable figures. Estimates are produced through survey weighting to align the sample with population controls from the decennial census, and they underpin much of the small area estimation work built on top of census geography.

The ACS is the primary source for detailed sub-county socioeconomic statistics used to calculate figures like the gini coefficient and the labor force participation rate, and it feeds funding-formula allocations and local planning by filling the gap between decennial censuses, which mainly count population and basic characteristics. A key pitfall: a 5-year estimate for a small geography represents an average across the whole five-year period, not a snapshot of any single year, and is unreliable for detecting a specific one-year change in a small area.

Last reviewed September 22, 2026

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Related terms

Census tract A small, relatively stable geographic area defined by a national statistical agency for reporting population data. Small area estimation (SAE) Statistical techniques for producing reliable estimates for areas or subgroups too small to sample directly. Gini coefficient A single number, from 0 to 1, measuring income or wealth inequality within a population. Labor force participation rate (LFPR) The share of the working-age population that is either employed or actively looking for work. Survey weighting Adjusting survey responses so the sample's demographic makeup matches the target population's known composition.

Related tools

U.S. Census Bureau Data Tools The Census Bureau's free official tools for accessing U.S. demographic, economic and geographic data, led by data.census.gov.

Related guides

Housing and community data, explained How housing markets and neighborhood conditions get measured — the indexes, the record-level data behind them and who publishes what for free. How to use census and government data Finding the right official statistics, joining them to your own data by geography, and the margin-of-error traps that catch first-time users. Where to find census and demographic data Government tables, harmonized microdata, and paid neighborhood segments each answer a different demographic question. Here is which one you need.