San Diego's population decline driven by immigration slowdown
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San Diego County's population shrank last year amid a massive drop in immigration, following a nationwide trend, new U.S. Census data shows.
Why it matters: The data offers the best look yet at how tighter immigration enforcement is affecting America's demographic makeup.
Zoom in: San Diego's population growth has slowed in recent years. That's partially because the city's high cost of living has forced locals out. In the past, immigrants moving in offset that drop — until last year.
- We saw the sixth-largest numeric population decline among U.S. counties in 2025, and experts say a continued slowdown could shrink the local workforce and economy.
By the numbers: San Diego County's population dropped by about 5,300, to 3.28 million people in 2025, the first year-over-year decline since 2021, according to the census data.
- That was driven by a 65% drop in net international migration following the Trump administration's crackdown on immigration, the Union-Tribune reported. It's the single largest decline in 15 years.
- Every one of California's 58 counties saw a drop in the number of foreign-born arrivals, and 30 saw population declines, per the U-T.
Between the lines: "The nation's largest counties ... are often international migration hubs," per Census Bureau demographer George M. Hayward.
- "With fewer gains from international migration, these types of counties saw their population growth diminish or even turn into loss."
The big picture: The U.S. overall still grew by 0.5% between 2024-25, but that's down from 1% over the previous period.
- Nationwide natural change (births minus deaths) held steady, while international migration plummeted from about 2.8 million people to 1.3 million.
- Caveat: The Census' international migration data include foreigners and Americans coming home from abroad, including military service members.