From the U.S. Census Bureau – For the past several years the Census Bureau has released data products from the American Community Survey (ACS) in the form of 1-year estimates. These estimates were based on data collected in a single calendar year and describe the average characteristics for that specific year. For example, the 2006 ACS estimates generally describe the average social, economic, demographic, and housing characteristics for calendar year 2006. Beginning in December 2008, the Census Bureau introduces ACS multiyear estimates, specifically 3-year estimates. These estimates are based on data collected over a 3-year period of time and therefore they describe the average characteristics for that 3-year time period. Both ACS 1-year and 3-year estimates can be accessed using the American FactFinder (AFF).
Please click here to view more information about these estimated from the U.S. Census Bureau.