Data and Methods: 2010-2020 Beta Release, April 2023
These data include estimates of net migration for US counties by five-year age group, sex, and various race categories each decade from the 1950s through the 2010s. The 1990s, 2000s, and 2010s also include estimates by Hispanic origin, and the 2010s include estimates for American Indians/Alaskan Natives and for non-Hispanic Asian/Pacific Islanders.
Net migration is the balance of in-migrants minus out-migrants. The data do not include flows of in-migrants or out-migrants, but only the net balance. Age refers to age at the end of the decade.
Estimates were generated using a residual method based on US Census counts at the beginning and end of each decade and intercensal birth and death records. The population counted at the beginning of the decade is aged forward over time, subtracting out deaths and adding in births, to generate an "expected population" at the end of the decade. The observed population counted in the census at the end of the decade is then subtracted from the expected population to estimate the number of net migrants. Net migration estimates were generated following this general process each decade by different research teams to create a coherent dataset spanning 70 years of age-specific net migration for US counties (see References below). Learn more about this method.
Because the estimates do not rely on sampling, they are highly accurate and reliable. Still, there are some limitations that users should consider. Estimates are less accurate for children under age 10, because birth records are occasionally recorded in the county of birth, rather than the county of the mother's residence. Estimates may also be less accurate at the oldest ages, due to challenges associated with death records. Breakdowns by race/ethnicity are less accurate than totals because of differences in how race/ethnic categories are recorded in birth records, death records, the decennial census, and the Population Estimates Program and changes over time. This is particularly true for the youngest and oldest age groups which are more dependent on birth and death records.
For the 2010-2020 decade, the delayed release of Census 2020 detailed results led the current research team to use the Census Bureau's 2020 "blended base" from its Population Estimates Program, vintage 2021, as the ending population in 2020. The use of estimates rather than enumerated data may have introduced problems that the researchers found in calculating net migrants and migration rates. In particular, the initial calculations for migrants ages 75 and older at 2020 seemed implausible. Furthermore, changes in race/Hispanic origin coding of births by the National Center of Health Statistics during the decade created unusual migration rates for children ages 0-9 at 2020 by race, particularly the American Indian/Alaskan Native population. As a result, the research team chose to make this "beta" release without data for ages 75 and over, and users are cautioned to not draw conclusions about the migration pattern of children under 10, especially regarding race and Hispanic origin. Once the Census 2020 data are released, the research team will review and revise as needed to provide the full complement of age, race and Hispanic origin estimates.
To facilitate comparison over time, the data for the 1950s through the 2000s that underlie the charts in this website combine some counties and county equivalents into groupings where boundaries have changed over time. Other counties are missing data from earlier decades. The geographic harmonization process generated 3,095 county observations plus 50 states (total n= 3,145); as of the 2020 Census, there were 3,143 counties plus the 50 states (and the District of Columbia). A summary of counties affected by these boundary changes is available. However, the estimates for the 2010s have not yet been harmonized with prior decades. As a result, users may encounter gaps in the maps and charts for certain counties.
You may also download the full dataset for the 2010s, including detailed documentation.
In addition to being available here, data from prior decades are available for download at ICPSR.
Sponsorship
Support for the generation of these data has come from various sources and institutions over the last 70 years. The 2010-2020 project, including construction of this website, was supported by Grant Number 1R03HD100772-01 from the Eunice Kennedy Shriver National Institute of Child Health and Human Development and by the U.S. Department of Agriculture, Economic Research Service, Cooperative Agreement No. 58-6000-9-0043. The content is solely the responsibility of the authors and does not necessarily represent the official views of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the National Institutes of Health, or the United States Department of Agriculture.
Work on the current project was conducted at the Applied Population Laboratory at the University of Wisconsin- Madison, the Department of Social Sciences at Michigan Technological University and the Carsey Institute at the University of New Hampshire.
Contacts
Please contact David Egan-Robertson at the Applied Population Laboratory with questions or comments about the data, any technical difficulties you may encounter, or to provide suggestions for improving this website.
References
1950s: Bowles, G. K. and J. D. Tarver. 1965. Net Migration of the Population, 1950-60, by Age, Sex and Color. Washington, D.C.: U.S. Department of Agriculture, Economic Research Service.
1960s: Bowles, G. K., C. L. Beale, and E. S. Lee. 1975. Net Migration of the Population,1960-70, by Age, Sex and Color. Washington: U.S. Department of Agriculture, Economic Research Service and Athens: University of Georgia.
1970s: White, M. J., P. Mueser, and J. P. Tierney.1987. Net migration of the population of the United States 1970-80, by age, race and sex. (Computer file with documentation.) Ann Arbor, MI: Inter-university Consortium for Political and Social Research.
1980s: Fuguitt, G. V., C. L. Beale, and P. R. Voss. 2010. County-Specific Net Migration Estimates, 1980-1990. ICPSR26761-v1. Ann Arbor, MI: Inter-university Consortium for Political and Social Research, 2010-04-02. doi:10.3886/ICPSR26761
1990s: Voss, P. R., S. McNiven, R. B. Hammer, K. M. Johnson, G. V. Fuguitt. 2004. County-specific net migration by five-year age groups, Hispanic origin, race and sex 1990-2000. CDE Working Paper No. 2004-24. Center for Demography and Ecology, University of Wisconsin-Madison. Madison, WI.
2000s: Winkler, R.L., K. M. Johnson, C. Cheng, P.R. Voss, and K.J. Curtis. 2013. County-specific net migration by five-year age groups, Hispanic origin, race and sex 2000-2010. CDE Working Paper No. 2013-04. Center for Demography and Ecology, University of Wisconsin-Madison. Madison, WI.
2010s: Egan-Robertson, David, Katherine J. Curtis, Richelle L. Winkler, and Kenneth M. Johnson, Age-Specific Net Migration Estimates for US Counties, 2010-2020. (forthcoming).
