Every Bay Area county is aging faster than the U.S.

We’re really aging, Bay Area. And fast.

The region grayed rapidly over the last decade, according to new Census data released Thursday, with the populations in all nine Bay Area counties outpacing the country in their upward median-age swing.

Marin County, our undisputed grandparent, shot up to a median age of 48.2 — a full decade older than the region’s young in Santa Clara County. After COVID started, San Francisco’s median age — meaning half the population is older and half younger — shot up 2 years to 40.5 in just two years.

Compare that to the United States’ median age, which climbed about 1.5 years from 2012 to 2022, according to the new Census Bureau data.

It’s the latest evidence of the region’s aging population that has also shown up in recent census reports, including a 38% spike in the number of residents 65 and older over the last decade and a 12% drop in youth 5 and under.

What’s behind the Bay Area trends? The explanations point primarily to one thing.

“We have one of the worst affordable-housing crises in the country, and one of the highest costs of living,” said Abby Raisz, research manager at the Bay Area Council Economic Institute, an economic policy think tank.

In Santa Clara County, experts say that the affordability crisis is offset by tech companies, which attract young families who keep the county’s population on the younger side. In other parts of the region, like Marin County, young people are being repelled by the sky-high cost of living and are not drawn back by compelling job prospects. In 2022, Marin had a median age more than 9 years above the national median.

Marin was almost 5 years older than the second-oldest Bay Area county, Sonoma, which had a median age of 43.3. Napa (42.9), San Mateo (41.3), Contra Costa (40.7), San Francisco (40.5), Alameda (39.3), Solano (39.1) and Santa Clara (38.2) round out the list.

San Francisco’s median age spiked almost 2 years after 2020, a direct link to the pandemic when young people who could work remotely fled big urban centers for more space.

When counties have a significantly older population, it can strain local resources. Seniors are less likely to work fulltime and therefore contribute less to income tax revenue, experts say. But at the same time, they rely heavily on public services, such as access to good health care.

“Cities and counties that don’t get ahead of this (aging trend are) … going to find themselves with a health care catastrophe as these older people don’t have access to the health services they need,“ said Matthew Lewis, director of communications for the pro-housing group California YIMBY.

And it’s not just a Bay Area problem.