Two factors influence population growth—natural increase and migration. These are generally described as the components of population change.

Census Bureau Migration Estimates and Flows

Migration Estimates

The Census Bureau tracks domestic migration (from other places within the United States) and international migration. Their estimates of international migration are comprised of: legal immigration from abroad; net undocumented immigration from abroad; emigration; and net movement between Puerto Rico and the U.S. mainland.

State-to-State and County-to-County Migration Flows

Since migration data are no longer collected as part of the decennial census, current migration flow data are available from the the American Community Survey. The survey asks 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.

IRS Nationwide Migration Flow Files

The State-to-State and County-to-County migration data are updated annually and based on the year-to-year changes in the addresses shown on the population of returns from the IRS Master File system. Excel files present data on migration patterns by state for the entire United States, including inflows and outflows. Aggregate money amounts are in thousands of dollars and median money amounts are in whole dollars.

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