These migration flows are derived from the household and group quarter locations sampled in the American Community Survey (ACS) and the responses to the migration questions on the questionnaire.

They are period estimates that measure where people lived when surveyed (current residence) and where they lived 1 year prior (residence 1 year ago). The data are collected continuously over a 5-year period to provide a large enough sample for estimates in smaller geographies. The flow estimates resemble the annual number of movers between counties for the 5-year period data was collected.

The flow files produced are:

• State-to-county — Available for the 2017-2021 5-year ACS data set.
• County-to-county — Available for the 5-year data sets starting with the 2006-2010 5-year ACS and ending with the 2016-2020 5-year ACS.
• County/minor civil division (MCD)-to-county/MCD — Provides flows between MCDs for the 12 strong-MCD states and counties in the other states. The strong-MCD states are states where the MCDs, a type of county subdivision, serve as general purpose governments and provide the same government functions as incorporated places. The strong-MCD states are Connecticut, Maine, Massachusetts, Michigan, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Wisconsin, and Vermont. These files are available for the 5-year data sets starting with the 2006-2010 5-year ACS and ending with the 2016-2020 5-year ACS.
• Metropolitan statistical area (MSA)-to-MSA —Available for the 5-year data sets starting with the 2009-2013 5-year ACS and ending with the 2016-2020 5-year ACS.

For selected data sets early in the series, the flow files have been crossed by social and demographic characteristics that vary by year. A characteristic will not be reused in overlapping 5-year ACS data sets. For instance, age was one of the characteristics for 2006-2010. Age flows will not be produced again until the 2011-2015 flows. These flows with characteristics are subject to suppression for disclosure avoidance purposes. County and county/MCD flows are suppressed if they consist of only one or two people in different households or group quarters. Complimentary suppression is used for the MSA flows.

Characteristics are not crossed with one another, and their universe may vary from one another and the universe for no characteristics, population 1 year and over.

Characteristics are included for the following years:

• 2011-2015 ACS: Age, Sex, Race, Hispanic origin
  
• 2010-2014 ACS: Relationship to householder, Household type, Housing tenure
• 2009-2013 ACS: Ability to speak English, Place of birth, Year in the United States (or Puerto Rico)
• 2008-2012 ACS: Employment status, Occupation, Work status
• 2007-2011 ACS: Educational Attainment, Personal income, Household income
• 2006-2010 ACS: Age, Sex, Race, Hispanic origin

The flow statistics are:

• MOVEDIN — The estimated number of movers from the reference county to the second county.
• MOVEDOUT — The estimated number of movers to the reference county from the second county.
• MOVEDNET — The estimated number of movers between the reference county and second county, or MOVEDIN minus MOVEDOUT.

For selected years, there are supplemental statistics files that provide summary statistics by mover type (e.g., nonmovers, movers to a state, movers from abroad). These flows crossed by characteristics are also subject to suppression. For the estimates based upon the population of the county 1 year ago, there must be at least 50 unweighted cases for the estimates to be shown.

For more information, please visit the Migration/Geographic Mobility page.