About 6.6 million U.S. households in 2009 had at least three generations of family members, an increase of 30 percent since 2000, according to census figures. When "multigenerational" is more broadly defined to include at least two adult generations, a record 49 million, or one in six people, live in such households, according to a study being released Thursday by the Pew Research Center.
The rise in multigenerational households is heavily influenced by economics, with many young adults known as "boomerang kids" moving back home with mom and dad because of limited job prospects and a housing crunch.
But extended life spans and increased options in home health and outpatient care over nursing homes have also played a role. So, too, has a recent wave of immigration of Hispanics and Asians, who are more likely to live with extended family.
"With the reality of 78 million baby boomers coming into an aging demographic, we need more housing choices for caregiving," said Elinor Ginzler, AARP's senior vice president for livable communities. "It can be a great opportunity for connectedness across generations, but also an opportunity for conflict if family members don't keep communications lines open."
An AARP analysis of census data shows that Hawaii had the highest share of multigenerational households, followed by California and Mississippi, due partly to a scarcity of affordable housing. North Dakota was least likely to have several generations living together.
Other findings from the Pew and AARP studies:
-The most common multigenerational family is an older parent who owns the house, living with an adult child and grandchild.
-Older women are more likely than older men to live in a multigenerational household.
-While multigenerational families are increasing, the number of adults 65 and older who live alone is edging lower, from a peak of 28.8 percent in 1990 to 27.4 percent in 2008.
Multigenerational households are not new. According to the Pew report, in 1900 about 57 percent of people ages 65 and older lived with extended family. Life in such a household was dramatized in the popular 1970s television series "The Waltons." Living in the Virginia mountains during the Depression, the Walton family had three generations under one roof, their togetherness symbolized by a round of goodnights that included teenage son and series narrator John-Boy.
After World War II, Social Security, Medicare and medical breakthroughs prompted healthier, more financially secure older adults to live on their own. By 1980 and 1990, just 17 percent of seniors lived in a multigenerational household.
The share of older adults in multigenerational homes is now increasing again, to about 20 percent.
"The government will continue to provide a social safety net for older adults, but given today's demographic and economic realities, it's not clear that this public safety net will be as robust in the future as it is now," said Paul Taylor, a co-author of the Pew report. "That could increase the trend toward family members providing care for elderly parents - a role that families have taken on throughout human history."
Today's multigenerational families include George Lee, 82, and his wife, Grace, 74, of Honolulu, who live in an apartment that is attached to a three-bedroom house occupied by their 50-year-old daughter, 61-year-old son-in-law and two college-age grandchildren.
While life isn't always perfect, the Lees say that everyone gets along well partly by carving out their own spaces, having a sense of fair play when it comes to household chores, and having separate front doors and kitchens.
"Because of the cost of housing in Hawaii, we felt that we needed to offer the kids housing so they can get a start on their careers and afford college," said George Lee, who with his wife rents the home to their daughter. "We actually sometimes go for a couple of weeks without bumping into each other, but we also do a lot of helping out with the grandchildren."