The American Community Survey (ACS) and the Puerto Rico Community Survey (PRCS) ask respondents age 1 year and over whether they lived in the same residence 1 year ago. For people who lived in a different residence, the location of their previous residence is collected.

ACS uses a series of monthly samples to produce estimates. Estimates for geographies of population 65,000 or greater are published annually using these monthly samples. Three years of monthly samples are needed to publish estimates for geographies of 20,000 or greater and five years for smaller geographies. The 5-year dataset is used for the county-to-county migration flows since many counties have a population less than 20,000. The first 5-year ACS dataset covers the years 2005 through 2009.

In addition to the county-to-county flow files, there are similar files that substitute minor civil divisions (mcd), in place of counties, for states where they serve as general-purpose local governments. These states are Connecticut, Maine, Massachusetts, Michigan, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and Wisconsin.

Starting with the 2009-2013 5-year products, additional metropolitan statistical area-to-metropolitan statistical area tables are included.

Census Flows Mapper: The Census Flows Mapper is an interactive, mapping application for the public to visualize and print, as well as download county-to-county flows. In the application, users select a county either by scrolling over it and clicking on the map or via drop-down menus. By default map will display net county-to-county flows into and out of the selected county. County-to-county flows may also be crossed by characteristics such as sex, race, Hispanic origin, and age. A PowerPoint Tutorial for the tables and Census Flows Mapper is available.

ACS Standard Tables

Inmigration and outmigration data are available for published geographies in data.census.gov. Detailed tables B07001 through B07013 contain geographical mobility in the past year for current residence by selected characteristics for all summary levels. The data are separated into five geographical mobility categories: Nonmovers, movers within the same county, movers from a different county within the same state, movers from a different state, and movers from abroad. Detailed tables B07401 through B07413 contain geographical mobility in the past year for residence 1 year ago by selected categories for some summary levels. The data are separated into four categories: Nonmovers, movers within the same county, movers to a different county within the same state, and movers to a different state. Tables dealing specifically for Puerto Rico have a -PR suffix and slightly different geographical mobility categories.

The Population Estimates Program publishes annual population estimates using various administrative and survey data. The program produces population, population change, and estimated components of change files for the nation, states, counties, metropolitan and micropolitan areas, and combined statistical areas as part of the datasets available for download. The files contain estimates for net internal and net international migration.