In a dramatic demographic shift largely fueled by staggering rent costs, more young adults in California and nationwide are living at home with their parents than they were a decade ago.

Nationwide, an estimated 24 million 18- to 34-year-olds lived in their parents’ home in 2015, an 8 percent increase from the previous decade, a Census Bureau report released Wednesday found. Every state in the U.S. saw an increase in the number of young adults living at home between 2005 and 2015 with the exception of North Dakota, which saw a 3.5 percent decrease.

And in California, the trend was even more pronounced. An estimated 9.3 million young people lived with their parents in 2015, a 10.2 percent increase in the past decade. Experts point to the high cost of living as a key reason for the shift, along with a desire by young adults to continue their education after high school before settling down to marry and have kids.

“Certainly the cost of living in the Bay Area has just skyrocketed,” said Laura Nichols, an associate professor of sociology at Santa Clara University. “And even though we have good-paying jobs in the Bay Area, they don’t necessarily translate into being able to buy a house or even paying for a down payment or first and last month’s rent.”

The study used data from the Census Bureau’s American Community Survey and the Current Population Survey to estimate the number of young adults living in their parents’ home.

Megan Joseph, executive director of the San Francisco-based organization Rise Together, said many families are being displaced out of the Bay Area — in particular San Francisco and Alameda counties — into other regions of the state, such as Solano and Contra Costa counties or the Central Valley.

“What that does for young people is that they’re moving from areas from where there are high opportunities to areas where there’s low opportunity,” she said. “It all comes down to the common denominator underlying all the displacement for young people and their families, which is cost of housing.”

Joseph said youth employment programs, access to affordable housing, and state and federal policy changes would be critical in reversing this housing trend.

“Right now it’s a strong trend and I don’t see it turning around quickly. It’s not a quick fix,” she said. “But it benefits all of us for young people to have opportunities.”

The report also found young men’s earnings have decreased drastically. An estimated 41 percent of young men aged 25 to 34 had incomes of less than $30,000 per year, compared with 25 percent in 1975, according to the report.

That’s partially due to the country’s shift from an industrial economy to one that relies largely on “pink collar” or female-dominated jobs, according to Nichols.

Meanwhile, a majority of young people in the nation have ditched the centuries-long tradition of marrying and having kids early in life to pursue educational and professional goals.

More than half of Americans believe marrying and having children are not as important for becoming an adult. In the 1970s, 8 in 10 people married by the time they turned 30, according to the report. In 2015, 8 in 10 people married by age 45.

“If one theme describes how adulthood has changed over the last 40 years, it is growing complexity,” the report said. “In 1975, there was one predominant adult milestone—family formation—that people largely experienced during their 20s. Today, while the milestones have remained the same, the pathways are more diverse.”