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2015-2019 ACS County-to-County Migration Files Documentation


The U.S. Census Bureau has been releasing county-to-county and county/minor civil division (MCD)-to-county/MCD migration flow estimates based on the American Community Survey (ACS) since 2012. 1 The first table package used 5-year ACS data collected from 2005 through 2009, the first ACS 5-year period.2 For sequential 5-year ACS datasets, tables were crossed by selected characteristics for the period of 2006-2010 to 2011-2015 datasets. The 2008-2012 release was the first time flows from Puerto Rico municipios to U.S. counties were included. Flows between metropolitan statistical areas (MSAs) were introduced with the 2009-2013 dataset.3 In addition, the county-to-county flows going back to 2006-2010 dataset are available through the Census Flows Mapper.4 As of 2016, all ACS migration flows data for counties, MCDs, and MSAs were made available in the Census application programming interface (API) through the Census Developers site.5 This year’s migration flows table package (based on 5-year 2012-2016 ACS) will deviate from previous years in that it will not include socio-economic characteristics, only basic flow counts.


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