The American Community Survey (ACS) is an ongoing survey that is conducted by the U.S. Census Bureau. Each month the survey is sent to approximately 300,000 randomly selected addresses (around 3.5 million addresses per year). The survey gathers information on demographics, educational attainment, jobs and occupations, housing characteristics, and other topics. These data are used by public officials and planners to learn about local communities and to distribute federal and state funds.
Individual survey responses are aggregated by the Census Bureau into estimates at many geographic levels. An ACS 1-year estimate includes data collected over a 12-month period and is limited to geographic areas with 65,000 people or more, while an ACS 5-year estimate includes data covering a 60-month period and is available for areas down to the block group (around 600 to 3,000 people). Geographic levels include states, counties, tracts, block groups, and other administrative and statistical entities. The U.S. Census Bureau defines census tracts as “relatively permanent” statistical subdivisions of a county that are “designed to be relatively homogenous units with respect to population characteristics, economic status, and living conditions at the time of establishment.” Census tracts generally encompass between 2,500 and 8,000 inhabitants.