What Has Driven Population Change in U.S. Counties?

Natural change (the difference between births and deaths), domestic migration and international migration all contribute to how an area’s population changes over time. Some have grown mostly through domestic migration while others have traditionally grown more through natural increase (more births than deaths).

However, in recent years the national pattern has shifted in substantial ways.

As the COVID-19 pandemic continues to amplify existing trends of decreasing births, increasing deaths and slowing international migration, shifts in the remaining component — domestic migration — have become more prominent and are noticeably altering county growth patterns across the nation.

The maps below illustrate how widespread these differences are.

Between 2015 and 2016, counties gaining population (in dark orange, dark green, or dark purple) were located across the country, with concentrations in the West, in Texas metro areas like Dallas and Houston, and in most of Colorado and Florida (Figure 1).

There was also a cluster of gaining counties in Tennessee, Georgia, North Carolina, and South Carolina.

In 65% of gaining counties, net domestic migration was the largest contributing component of change in absolute terms.

Counties shaded light orange, light green or light purple lost population between 2015 and 2016.

As the map shows, many of the areas that lost population (in parts of the Great Plains, the Rust Belt, and the Mississippi Delta), also did so largely because of net domestic migration.

In some parts of the country like Maine, southwest Virginia and West Virginia in Appalachia, the biggest component was natural change.

Fast forward to 2020 to 2021, and you can see a widespread change in these patterns.

During this period, more than half of counties (58%) gained population; domestic migration was the major component of change in 90% of them.

The role natural change played in 2020-to-2021 population shifts is also clear: A large swath of counties that lost population mostly because deaths outnumbered births stretched through Appalachia from southwest Virginia all the way to upstate New York.

Although natural decrease (where deaths outnumber births) wasn’t always the largest component, it occurred in 73.1% of counties — a record high.