The U.S. Census Bureau released the first county-to-county migration flow estimates based on the American Community Survey (ACS) in April 2012. It used data collected from 2005 through 2009 that composed the first ACS 5-year dataset. The ACS program combines consecutive yearly datasets to increase the sample size and provide reliable estimates for smaller areas. Even though estimates are produced for 1-year and 3-year datasets, estimates are only published for geographic areas of 65,000 and 20,000 population, respectively. Only the 5-year datasets provide estimates for all counties and county equivalents in the U.S.

This release consists of the same tables using 2006-2010 ACS 5-year data. Additional tables are added to the table package for certain characteristics: age, sex, race and Hispanic or Latino origin. Besides county-to-county migration flows, the table package also contains flow data for minor civil divisions (MCD) for a few select states in which they are commonly used as the primary substate aggregate unit instead of counties.