Domestic out-migration from urban counties accelerated last year, but slowing international migration contributed more to the loss in urban counties, which shrank by 0.3 percent. Urban population growth has been slowing since 2012. It rebounded in the Great Recession, as cities became more affordable and as the foreclosure crisis hit many suburban and exurban areas. But growth rates slowed throughout the 2010s, in part because many cities built too little housing to accommodate newcomers. That slowdown turned to population losses, and in 2020 urban counties shrank at an even faster rate than that of the small-town and rural counties outside metropolitan areas. Domestic migration drives most local population change, meaning the places that draw new people from elsewhere in the country grow the fastest. In most places, the other two components of population change — international migration and “natural increase” (births minus deaths) — have much less effect on local growth and decline. Among the 10 fastest-growing larger metros in 2020, all gained more domestic movers than they lost. Yet Boise, Idaho, and Provo-Orem, Utah, gained few people from international migration, and Cape Coral and North Port, Fla., had more deaths than births because of their older populations.