Adult children are moving back in with parents, and grandparents are taking up residence with their kids' families. Sound like old times? In fact, multi-generational households are making a comeback, according to a report released today.

Some 49 million Americans now live in such an arrangement, up from 28 million in 1980.

The tight-knit families could be the result of both social and economic factors, including the recession but more broadly reflecting a years-long trend, according to study researchers from the Pew Research Center's Social and Demographic Trends project.

The finding extends previous research. Pew research out last year suggested 13 percent of parents with grown children had an adult son or daughter who had moved back home over the past year to take refuge from the dim economy, among other reasons.

The new study involved telephone surveys conducted in February and March 2009 with a nationally representative sample of 2,969 adults living in the continental United States.

Multi-generational family households were defined as: two generations (parents or in-laws and adult children ages 25 and older); three generations (parents or in-laws, adult children and grandchildren); skipped generation (grandparents and grandchildren, without parents); and more than three generations.

Flip-flop

Between 1980 and 2009, there was a 33 percent increase in the share of Americans living in multi-generation households. Just the opposite was found in the decades' prior. For instance, from 1940 to 1980, that share had declined by more than half, from 25 percent in 1940 to 12 percent in 1980.

Demographic factors, such as growth of the nuclear family-centered suburbs, contributed to the falling out of grace of extended family households, Pew reports suggest.

As for the recent growth in such households, Pew researchers say it's partly the result of demographic and cultural shifts, including the increasing proportion of immigrants (who are more inclined than native-born Americans to live with multiple generations), and the rising median age of first marriage of all adults.

On average a guy marries for the first time at age 28, while a typical women ties her first knot at 26. The ages are about five years older than in 1970, Pew researchers say. The result: More unmarried 20-somethings in the population who might be drawn to their childhood home as an attractive living situation.

That's especially true in the weak economy, as high unemployment and rising foreclosures are driving individuals from different generations to double up under the same roof, the researchers say. In fact, from 2007 to 2008, the number of Americans living in a multi-generational family household grew by 2.6 million. No age group is immune. For instance, about one-in-five adults ages 25 to 34 now live in multi-generational households. (The recession began in December 2007.)

Who is affected
This trend has affected adults of all ages, especially the elderly and the young. For example, about one-in-five adults ages 25 to 34, and the same proportion of the 65 and older group, now live in a multi-generational household.

The shift has impacted adults of ages – the elderly, the young, and those “sandwiched” in middle age.  
 Among the elderly, there has been also been a different, but complementary trend change. After rising steeply for nearly a century, the share of adults ages 65 and older who live alone flattened out around 1990 and has since declined a bit. The report explores the reasons for this trend reversal. Using our own survey data, it also examines the differences in overall happiness, health, well-being and various life experiences between older adults who live alone and those who live with others.

At the other end of the living-arrangement spectrum, single-person households have also increased over the past century. In 1900, just about 1 percent of Americans lived in such a household, compared with 10 percent by 2008.

Among those ages 18 to 24, just 4.6 percent live by themselves, down from 5.7 percent in 1980; for adults ages 65 and older nearly 6 percent lived alone in 1900 compared with 28.8 percent in 1990 and 27.4 percent in 2008.

The bump might not be a good sign for the well-being of those flying solo. According to a Pew Research Center survey conducted last year, adults ages 65 and older who live alone say their health is worse and they are more like to feel sad, depressed or lonely than their counterparts living with a spouse or other family member.

But that's open for debate, as a recent study using data from the General Social Survey found Americans grow happier with age