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SAN FRANCISCO (KRON) — A new study reveals a “dramatic” shift in population size in San Francisco during 2020.

Net exits from San Francisco increased by 649% when California Policy Lab looked at data from the end of March 2020 to the end of the year, compared to the same period one year earlier.

But the research published Thursday shows the county is alone in this mass exodus compared to the rest of California.

In fact, many of these ex-San Francisco residents flocked to nearby areas.

CPL said about two-thirds of those leaving stayed in the Bay Area. Many also moved to counties near the Sierra Nevada mountains and other parts of Northern California.

And the people who left aren’t being replaced by nearly enough newcomers to make up the difference compared to prior years — which may be because many major businesses are not requiring new employees to relocate immediately.

According to CPL, 61.3% more people left San Francisco during the last quarter of 2020 than they did in the last quarter of 2019 — and 24.6% fewer people moved in during that period compared to the prior year. Eighty percent of the San Francisco migrants remained in California.

CPL research fellow Natalie Holmes said California “clearly” did not experience a mass exodus. “At the county level, however, San Francisco is experiencing a unique and dramatic exodus, which is causing 50% or 100% increases in Bay Area in-migration for some counties in the Sierras.”

See the entire Bay Area region’s moving in and out rates below for the fourth quarter of the year, via CPL:

As seen, neighboring San Mateo County is the second-most-fled county in the Bay Area, but San Francisco’s rates still far surpass San Mateo’s increase of 28.6% more exits in 2020 compared to 2019.

Researchers said they tracked the California migration patterns using changes in ZIP codes from one quarter to the next. Addressing concerns about wealthy residents leaving the state, CPL said there is no evidence that COVID is causing residents of wealthy places to leave en masse.