Barack and Michelle Obama have very busy schedules, of this there is no doubt. It’s a good thing they have some help, not just from staffers, but also from family: Michelle Obama’s mother, Marian Robinson. Before her arrival, the last presidential grandmother to occupy the White House was Elvira Doud, Dwight Eisenhower’s mother-in-law.

Fewer American families live like this today than in 1953. But according to a new report from the Pew Research Center, multigenerational households are becoming more common. In 1980, some 12 percent of families had two or more adult generations living under the same roof. Now, 18 percent do, and the total number of Americans with this living arrangement has doubled, to 56.8 million. Almost half (48 percent) are in households that working parents share with luckless “boomerangs” sheltering in their old childhood bedrooms. But nearly as many are living with three generations or more. In fact, 20 percent of Americans age 65 or older live in multigenerational households, compared to 16 percent in 1990.

Economics and culture help explain why. There is a glut of unmarried, underemployed young adults who could use their parents’ help. And young couples are increasingly finding that having parents join their households makes economic sense. For one thing, it is a real boon for working couples with kids, Steven Mintz, a sociologist at the University of Texas at Austin, points out. Mintz’s mother-in-law lives with his family. Having another adult to help with child care and cooking frees up working-age parents in demanding careers, and for Mintz’s family, it has made theirs feel “closer and more integrated” than it would otherwise, he says. More broadly, it’s cheaper to run one household than two, and the need to save is still keenly felt after the recession. Some newlyweds are delaying or eschewing home buying (and some who did become home-owners suffered a massive case of buyer’s remorse post-recession). Many young families have parents with large houses—bought for a song in cheaper, more booming times—with plenty of room to share.

Moreover, many retiree baby boomers—let’s call them “boomerees”—say they would like to be close to family. For an earlier generation, retirement meant a secluded Sun City with a golf course, far from offspring. But “today’s retirees report wanting to stay in their communities and engage with younger generations,” says Donna Butts of Generations United, a family research nonprofit and advocacy group. Boomer grandparents dote on grandchildren, and increasingly care for them. Intergenerational affinity between parents and children is high. “People actually like each other,” says Butts—some enough to live under the same roof.

An increase in the number of immigrants over the past several decades has also boosted the number of multigenerational households. Outside the United States, living this way is common, and families continue the practice even after moving here. Non-native-born Americans are more likely to live with three generations; some 14 percent of Asian Americans do so. It is also not uncommon among blacks and Latinos, whose median family incomes are lower than the American average and whose share of single parents is higher. Each of these minority groups is growing, and more homes with three generations are apt to come.

This is not to say that such households are common. Though the number of Americans living this way is rising, the overall portion of this type of household is still extremely small—just 5 percent, according to census data—and has not changed dramatically in the last decade. When the Eisenhowers moved into the White House, about one-quarter of older Americans lived with their children. In an earlier century, more than 60 percent of elderly white people lived with members of a younger generation, according to Steven Ruggles of the University of Minnesota. Living together was necessary in an agrarian society, but older generations had tremendous power over younger ones: You had to behave yourself to inherit the farm. It was good for the old and oppressive for the young, especially daughters—“a horrible time,” says Ruggles. Industrialization opened up labor markets, and grown children could escape to the cities, earn independent wages, and set up their own homes. (Mom and Dad on the farm could go and fend for themselves.) In the 20th-century post-war years, cities boomed and suburbs full of nuclear-family homes followed.

That sense of independence runs particularly deep for the most senior baby boomers (those born around 1946) and the generations preceding them. “Especially,” observes Nancy Thompson of the AARP, among “those of us who were among the earliest group of women in this country to work steadily outside the home.” Thompson is a grandmother, and her children have asked more than once whether she would like to live with them, but she has demurred. “I don’t think it would be good for anyone for me to meddle in their lives or they in mine,” she says. (It reportedly took some coaxing to get First Granny Robinson, born in 1937, to come live with the kids.)

But demographics and social factors point to more in multigenerational living in the long term: Increased acceptance feeds greater prevalence, and vice-versa. Baby boomers young enough to have boomerangs in the basement might not see sharing a house as so out of the ordinary when they leave the workforce and become boomerees. Their children also have a deeper sense of responsibility for caring for aging parents than older cohorts did, according to an earlier Pew study. Boomerangs, remembering the warm bed and home-cooked meals in their struggling years, might be more inclined to repay the favor when Mom and Dad could use some help. (Lennar, a savvy housing developer, has already been building “Next Gen” homes for two families with this living arrangement in mind.) It is surely not for everyone, but with child care costs soaring, and aged care also getting costlier (the average assisted-living home is now $42,600 a year), it could be worth the annoyance of a few more episodes of The Price is Right playing on the living room television.