But many of these counties … are feeling the brunt of the nation’s low birthrate.
….
Altogether, the nation’s 20 largest counties gained more than 300,000 new residents between July 2021 and July 2022 through international migration, which consists mostly of immigrants but includes anybody that moved to the US from overseas.
For some of these counties, such as San Diego, Miami-Dade, and King County in Washington, which includes Seattle, immigration stabilized the population numbers, which otherwise would have decreased.
Source: Immigration tripled in top US counties even as many of them lost population
