More millennials are living at home than at any other point this century, according to Zillow.

The number of adults aged 23 to 37 staying or returning home to their parents has been steadily rising since 2000.

Experts say the unaffordable housing market is keeping millennials at home, rather than a failure by millennials to hold jobs or launch careers.

Thanks to student loan debt, rising rents and stagnant wages, more millennials are living at home with their parents than at any other point this century.More than one in five adults, or 22 percent of millennial Americans, are either staying home or returning to childhood bedrooms, according to Zillow.

That number has been increasing steadily for the past two decades, and it's nearly doubled to about 22 percent of people ages 23 to 37 now living with their folks from 11.7 percent of people the same ages back in 2001. While it's easy to point fingers at the "boomerang" generation, experts say the reasons behind returning home for adults in this generation are due to more than a failure to "adult."

More millennials hold jobs than they did directly in the aftermath of the financial crisis, indicating that millennials are struggling to afford homes even as the economy recovers. Student loan debt has risen, housing costs have skyrocketed, and wages have stagnated — though the last is recently showing some signs of relief.

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While the housing market is growing more moderately than it has in the past, homes are still unaffordable in more than 70 percent of America when comparing median home prices to median income across counties nationwide, according to a recent ATTOM Data Solutions report. Nationwide, median rent rose 2.4 percent to reach $1,472 in February, according to Zillow. Median home prices in the nation rose 7.2 percent in February to $226,300.

All of this is compounding anxiety for millennials who, as they get older, grow wary that they are relying too much on their parents and are falling behind their peers. More than half of younger millennials say they can't keep up their lifestyles without help from their parents, according to a report from Merrill Lynch.

It's also why 75 percent of early adults are defining success as financial independence from their parents, as opposed to building wealth and accruing assets for themselves.

Living at home with mom and dad also comes with its perks: Millennials who want to save enough for a down payment on a home can afford to nearly three years sooner if they stay at home, Zillow's apartment search platform HotPads found.

The Zillow report that a small number of millennials — less than 2 percent — are also housing parents in their own homes, either to take care of them or as live-in child care for their own children.

Among metros with the largest share of millennials living at home: Los Angeles, Miami, New York City and Riverside, California. At least 31 percent of millennials live with their parents in those metros, all of which are among the least affordable rental markets in the country.

For example, more than three out of 10 millennials live at home with their parents in Los Angeles, where median rent prices eat up over 45 percent of median income.

Conversely, millennials are least likely to live with their parents in cities like Seattle, Austin, Portland, Kansas City and Denver. However, because those cities are also expensive rental markets, millennials are likely not living with parents because their families are too far away.