American Community Survey
The American Community Survey (ACS) is an annual nationwide survey designed to supplement the decennial census. The survey, based on the decennial census long form, produces population and housing information every year instead of every 10 years. Annual estimates of demographic, social, economic, and housing characteristics are available for geographic areas with a population of 65,000 or more. This includes the nation, all states, the District of Columbia, all congressional districts, approximately 800 counties, and 500 metropolitan and micropolitan statistical areas. Multi-year estimates are available for smaller geographic areas. During the demonstration stage (2000 to 2004), the U.S. Census Bureau carried out large-scale, nationwide surveys and produced reports for the nation, the states, and large geographic areas. The full implementation stage began in January 2005, with an annual housing unit (HU) sample of approximately 3 million addresses throughout the United States and 36,000 addresses in Puerto
Rico. And in 2006, approximately 20,000 group quarters were added to the ACS so that the data
fully describe the characteristics of the population residing in geographic areas.
http://www.census.gov/programs-surveys/acs/ and related web pages.