Millennials living in their parents’ basement have become a common trope used to illustrate the challenges young people face in today’s economy. But a new study suggests that about one-quarter of those young adults living at home are doing so due to something other than economics

One in four 25- to 34-year-olds who live at home — about 2.2 million young adults — are neither working nor in school, according to a report released Wednesday by the Census Bureau. This group is more likely than their other young adult peers living at home to have a disability or a child. Overall, 24 million millennials are still living in their childhood home.

“They may be living at home because they’re supporting or caring for a family member,” said Jonathan Vespa, a demographer who authored the report. “It may not necessarily be because of an economic reason that they’re not in school or not working, it could be a health related reason or it could be a caregiving reason.”

The latest findings help to illustrate the varying experiences of so-called boomerang children, which now represent the most common living arrangement for young people. Overall, the share of 18-to-34-year olds living with their parents has climbed from 26% in 2005 to 34.1% in 2016. For the bulk of this group, living at home is a reflection of their economic circumstances, Vespa said. Roughly 81% of 18- to 34-year olds living at home are either working or in school and they’re less likely than their other young adult peers to have a bachelor’s degree or a full-time, year-round job.

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In other words, as the Census report notes, this group is “working towards a firmer footing” before setting up their own household. That reflects other findings in the study, which indicate that Americans today value education and economic stability as markers of true adulthood.

Of course, it’s cheaper to live at your parents’ house. More than 20% of millennials lived with a roommate as of 2015, a study released by real-estate website Trulia earlier this month found, but many others are holding off on rent and still living at home with their parents. About 30% of your income has long been considered the maximum people were supposed to spend on rent, but these days the median amount renters — many of whom are in their 20s and 30s — spend across the country is almost 40%.

The focus on education and financial stability as rites of passage distinguishes Americans’ attitudes today from those of prior generations. In 1975, about 45% of 25- to 34-year-olds lived with away from their parents, had been married, had a child and were working. Now, just 24% of young adults have met all four of those milestones. The second most common lifestyle for young people is to be living away from home and in the labor force, but without a spouse or child.

“The change in the milestones that young adults have completed goes hand in hand with looking at American attitudes and values,” Vespa said. “Americans overall tend to rank educational and economic accomplishments very high and as very important parts of becoming an adult.”