The retirement years sometimes are seen as a return to the time before the birth of children. A time for empty-nesting, and potentially downsizing because all that space in the house—not to mention the rusting backyard swing set—is no longer needed.

But before you start constructing retirement plans around that vision, factor in the chances that you’ll need to financially support a child or children at that point in your life, potentially to include living with you.

That’s the message of a study by the Pew Research Center, which documented the trend of young adults returning to their parents’ homes after a few years away due to college, military service or having struggled to make it financially on their own.

The current under-30-or-so generation sees little of the stigma that previously was attached to living at home as a young adult, it found. During the 1970s the percentage of persons aged 25-34 living in a multi-generational household (the large majority of which consist of adult children living with their parents) bottomed out at around 11-12 percent. After rising a bit in the following two decades it has shot up in recent years to 22 percent. Those numbers reflect only long-term living arrangements and don’t include the additional short-term move-ins.

The report cited the obvious factors that go into such a decision, including inability to find employment that pays well enough to maintain an independent household. “Adults in their late 20s and early 30s have fared somewhat better in the labor market, but they have felt the sting of tough economic times in other areas of their lives. Many have had to settle for jobs they didn’t really want just to make ends meet. Fully a third have gone back to school, and an equal share (34 percent) have postponed either marriage, parenthood or both,” it said.

About half of boomerangers pay rent to their parents and about nine-tenths say they help with at least some household expenses.

“In some cases, the economics of multi-generational households can be beneficial for both adult children and their parents. While many young adults help defray their parents’ household expenses, living with mom and dad can also be a financial lifeline. In 2010, the poverty rate for young adults ages 25 to 34 who lived in multi-generational households was 9.8 percent. This compared with a poverty rate of 17.4 percent among young adults living in other households,” said the report.

Continued financial dependence goes beyond continuing to living at home. Overall, 38 percent of those in that age group say their own financial situation is linked to their parents’ financial situation, with 18 percent saying the two are connected to a great degree. Not surprisingly, the connection overall is more a positive for the younger person rather than a negative. About a tenth in that age group regularly receive money from their parents.

Apart from the issue of money is the status of the relationship, and here opinions are equally split. Among those ages 25 to 34, 24 percent say living at home has been good for their relationship with their parents, 25 percent say it’s been bad for it, and the rest say it hasn’t made a difference. Since the survey was only of people in that age group, the report didn’t include the parents’ opinions.

Whether you would view it as a positive or negative, large or small, don’t discount the chance that as a retiree you’ll be hearing the pitter patter of big feet around the house.