– After graduating from college in 2014, Dean Pearce, 24, weighed why he should or shouldn't continue to live with his parents. His conclusion: "The 'pro' is: You're never alone. The 'con' is: You're never alone."

Ten years from now, Pearce hopes to have a law degree and be a New York City attorney living with his girlfriend, who is in law school now. Meantime, Pearce is studying for his LSATs and working full-time at a coffee shop, while living with his parents in suburban Chicago.

More than 20 percent of millennials (born 1981 to 1996) are living with mom and dad, even though they have graduated from high school or college, according to the National Association of Home Builders' 2016 "Missing Young Adult Households" study. That's up from 12 percent in 2000.

"We call it the 'Great Delay,' " said Stephen Melman, the NAHB's director of economic services. "Instead of buying their own homes like their parents did at this age, they're living at home until they get married, at least."

Not all millennials who move out stay out. About 55 percent of them "boomerang" back to their parents' home by age 27, according to the Bureau of Labor Statistics' National Longitudinal Surveys program, which has been tracking a group of 9,000 people from this generation since 1997. Most likely to boomerang are women, Caucasians and college graduates.

"I had an apartment in Chicago," said Meghan Kennihan, 34, a running coach and personal trainer who lives in her folks' finished basement in the suburbs. "It was tiny and expensive. I was miserable. I moved back. Now, I have a bedroom plus an area for my scrapbooking hobby and another for my exercise equipment. It's like having my own apartment except I have more space than I can afford to have in an apartment."

Homebuilders and real estate agents increasingly see millennials influencing home purchases.

"One of out six of our buyers have or plan to have a grown child at home," said Richard Bridges, Chicago division sales manager at David Weekley Homes, which is building single-family homes and townhouses in the Chicago suburbs. "They're not kicking them out. Many anticipate their aging parents moving in at some point, too. They want a premium location — near public transportation and employers — and don't want to have to move again when the family changes."

For a minimal added cost, these buyers put one of their bedrooms on the first floor so the grown child or grandparent is separate from the rest of the family, Bridges said. Or, for $35,000-plus, they include a bedroom-and-bathroom suite in a finished basement.

No matter the floor plan, it helps when parents and their millennials get along.

"My parents have done so much for me, and now they're letting me live here rent-free, so I try to help out," said Pearce. "I pick up my sister from school, do the dishes or whatever chore needs to be done. My mom makes dinner. We all work as a team."

Kennihan contributes toward household expenses by paying rent. She does the laundry and keeps the fridge stocked. "And I 'babysit' the house while my parents visit my twin sister in Pennsylvania or my brother in Ireland," she said.

The No. 1 reason kids return to the pads from which they were launched: money.

Since 2006, a millennial's median annual income increased only $700, said the "Missing" report. Home prices continue to climb. Many a millennial doesn't want to get a mortgage until the college loans are paid back. And self-employed millennials like Kennihan are handcuffed by hefty health insurance premiums.

If nothing else, the trend strengthens family bonds that will be tested again when the aging boomer parents are unable to be independent. Said Pearce of his folks: "When they need help, I hope they can move in with me."