As more adults decide to live with mom and dad, young men appear to be less willing to fly the nest than women, a new study finds. This, experts say, could be an early sign of larger economic problems.

Millions of young Americans are living at home, according to a Pew Research Center analysis of U.S. Census Bureau data. The number of “millennials” -- adults aged 18 to 31-- living at home rose to 36% last year. That represented the highest percentage in the last four decades, and a significant increase from 32% just five years earlier. In 2012, 56% of adults aged 18 to 24 lived in their parental home, Pew found, as did 16% of adults aged 25 to 31. However, millennial males (40%) were significantly more likely than millennial females (32%) to live with mom and dad.

There are some demographic reasons for the gender gap. On average, men tend to marry later than women, says Zhenchao Qian, chair of sociology at Ohio State University. “There are more single young men than women out there,” he says. “This gives unmarried men more time to live with their parents.” Men marry at around 29 years of age, approximately two years older than the average for women, and both sexes are marrying around two years later in life than two decades ago, according to a 2012 survey by Bowling Green State University’s National Center for Family and Marriage Research in Ohio.

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Perhaps a more controversial theory: Sons may also have an easier time at home. Even in 2013, parents expect their sons to do less housework than their daughters, Qian says. “Parents give their sons more freedom than their daughters,” says Kit Yarrow, chair of the psychology department at Golden Gate University in San Francisco, Calif. and co-author of “Gen Y.” For Americans aged 18 to 24, “it’s easier for a young man to live at home and still feel independent than it would be for a young woman,” she says. An even less flattering reason: “Women tend to mature, emotionally, faster than men.”

Also see: 10 things Generation Y won’t tell you.

But there are more worrying factors in play than a taste for the comforts of home, says John Bonini, content marketing manager of Impact Branding & Design in Wallingford, Conn., who regularly carries out research on millennials. Women have consistently outnumbered men when it comes to college enrollment, he says. “Since the economic downturn, with many state and local governments cutting spending, and manual labor jobs doing the same, it would make sense that those with college degrees would see a greater chance of gaining employment than those without one.” Many young men, he says, are getting left behind.

Young women tend to outperform men in post-secondary education. Some 71.3% of female high school graduates in the class of 2012 enrolled in college versus 61.3% of males, according to the government’s Bureau of Labor Statistics. The former also appear to be better students. “Females tend to finish college faster than males,” according to the Pew report. What’s more, men who had earned bachelor’s degrees in 2011 had an unemployment rate of 16.1% in October 2011, compared with 11.2% among females, a separate Bureau of Labor Statistics report found.

Regardless of sex, children living at home longer put a bigger financial burden on their parents and the economy. Hosting a son or daughter after 18 can cost $8,000 to $18,000 a year, according to a recent report in the Wall Street Journal. And the fact that around 22.6 million young adults are still living at home also means there are fewer renters and potential buyers of first-time homes in the property market. Only 450,000 new households are being created annually versus 1.1 million before the recession, according to real-estate marketplace Trulia; 18- to 34-year-olds make up half of that demand.

See more: “The kids aren’t buying homes.”