The American Community Survey (ACS) is an ongoing statistical survey conducted by the US Bureau of the Census. The survey is mailed to approximately 250,000 addresses monthly. It regularly gathers information previously contained only in the long form of the decennial census. The 2010 US Census changed sigificantly from earlier censuses. Due to rising costs, the census form was reduced to ten (10) questions, consequently the amount of social-demographic data that was once collected was no longer available. The American Community Survey is the Bureaus effort to provide some of the data that was lost due to the change.
Each year the American Community Survey sends approximately 3 million surveys to housing units and group quarters in the United States, in every county, American Indian and Alaska Native area, Hawaiian Homeland, and in Puerto Rico. Data are collected primarily by mail, with Census Bureau telephone and personal visit follow-up.
The processed information provides annual estimates for all states, as well as all cities, counties, metropolitan areas, and population groups of 65,000 people or more. For smaller areas, it is necessary to combine multiple survey years to obtain reliable estimates: three survey years in areas with 20,000 to 65,000 people, and five survey years in areas with fewer than 20,000 people. Consequently, the level of detail at for geographical areas is no longer available. The quality of these samples was originally intended to match that of the decennial census long form, but because the sample size of the American Community Survey is smaller than originally expected, American Community Survey estimates are less precise than the comparable estimates from Census 2000 and prior decennial census years.