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California is getting older, except in this county

Students cycle on the campus of UC Davis. | Nick Otto/Washington Post via Getty Images
Students cycle on a University of California campus. | Nick Otto/Washington Post via Getty Images | Source: Nick Otto for the Washington Post/Getty Images

A new California county has become the state’s youngest, even as many others—and the state and country as a whole—age around it, according to newly released census data.

The median age of Yolo County dropped to 31.5 years in July 2022. Sitting west of Sacramento and home to University of California Davis, the rural, agricultural region is now the most youthful county in the state. Yolo narrowly beat out the Central Valley counties of Merced and Tulare, where the median age sits around 32. 

Meanwhile, California’s median age climbed from about 37 to nearly 38 in the two years leading up to July 2022, according to U.S. Census Bureau estimates. The state’s population has been aging for years, following a nationwide trend. 

That’s largely because California’s population of children has been shrinking, said Population Reference Bureau Demographer Beth Jarosz. Researchers say a society is at a “replacement rate” when families have two kids, thus replacing the parents. 

“We’ve been below that [replacement] rate for quite a long time,” Jarosz said.

The leading theories as to why the state’s birthrate has plummeted revolve around whether or not young people feel like they have the resources to take care of a family, Jarosz said.

“A lot of families really seriously consider whether or not to have a second or third child given how expensive housing is in California and nationwide,” she said.

From Mountain Towns to Farmland

There’s a vast difference in age distribution across California communities. The oldest California county has a median age of nearly 54, dwarfing Yolo’s median of 32 years, according to the census data.

A county’s age profile is driven by the type of people attracted to live there, Jarosz explained. Sierra County, the state’s oldest, sits at a high elevation, between the Tahoe and Plumas national forests. That’s typical of the state’s older regions, many of which are “gorgeous mountain retirement destinations,” Jarosz said.

Meanwhile, Central Valley counties draw in seasonal farmworkers, many of whom are younger than the retirees fleeing for the state’s snow-capped peaks.

In the Bay Area, rural, wealthy Marin County is the oldest, with a median age of 48. Santa Clara County, home to Stanford University and scores of young tech workers, has the lowest median age: 38 years.

San Francisco Also Aging

San Francisco is growing older; its median age rose from about 39 in July 2020 to about 40 years in July 2022.

Despite that, the largest age group in the city is 30- to 34-year-olds. About 88,000 San Franciscans fell in that age range in July 2022, representing about 11% of the city’s population. That’s despite the city losing about 15% of residents in their early 30s between July 2020 and July 2022.

The city’s largest loss of any age group since the first year of the pandemic was among 25- to 29-year-olds. There were nearly 18,000 fewer San Francisco residents in that age bracket in July 2022 than in July 2020, a remarkable 19% decline.

Adults aged 70 and older were the only age group that grew in San Francisco during the Covid years.

How Old Is Your County?

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Noah Baustin can be reached at

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