The recently released 2008 American Community Survey (from the U.S. Census Bureau) finds about 4 million “multigenerational” American households, reports the Houston Chronicle. This trend seems to be enjoying renewed popularity, sociologists note:

While the number of multigenerational households has remained steady since the 2000 Census, sociologists and demographers say they expect to see an increase. Immigration and out-of-wedlock childbearing generally spur high rates of multigenerational households in certain geographical areas, and they will continue to be factors, experts said.

What’s pushing the trend now is the recession and baby boomers. With layoffs and furloughs, people are moving back in with their parents or other family members to save money. Also, many baby boomers are taking care of their elderly parents as the cost of long-term care soars. Baby boomers themselves are growing old, too. Their children will be preparing to take care of them, experts said.

“People are going back to living the way they did in the beginning of the 20th century,” said Ray Eve, head of the sociology department at the University of Texas at Arlington.

Eve said economics was a driving factor then, just like it is now.

This illustrates how the idea of “family” shifts over time:

Society has had a long fascination with the idea of the traditional family — father, mother and children — but the reality is it has never really existed, said Holly Heard, a sociology professor at Rice University.

People often have lived with extended family members, and they do more so now than 20 years ago, Heard said.

For the early part of the 20th century to the 1950s, multigenerational households were fairly common. After World War II, people became more affluent, and family members moved out because they could afford to live on their own. A shift began to occur in the 1980s, when the recession hit, sociologists said.

Despite the day-to-day challenges that may come with three or more generations sharing one home, sociologists note benefits, as well:

Studies show some physical and psychological benefits for multiple generations living together, sociologists said.

People who live with relatives tend to have better health and are less suicidal. Children are also less likely to be delinquent because they have additional family members to nurture and take care of them, they said.

Explore more housing data from the American Community Survey.