In the 1930s, Thomas Wolfe wrote a best-selling American novel entitled, You Can't Go Home Again. It's a sentiment many agree with. Once you leave home, they say, it's difficult, harmful, and maybe even unnatural, to come back. Yet the U.S. Census estimates that as many as 20 million men and women, ages 18 to 34, live at home with one or more parents. Those who once left but have come back are called boomerang kids.

They discovered that living on your own can be difficult, especially on a low salary. Marriages or other relationships break apart, or things may not go well in college. So they knock on Mom and Dad's door, believing they'll be staying only a few months at most.

One family therapist, Cynthia Graves, has written that boomerang kids stride into adulthood thinking they're entitled to the good life: a house, two cars, nice vacations. When they discover that getting these things is not easy, they run up huge amounts of credit-card debt and end up back with Mom and Dad because they cannot pay the bills.

If you ask them, of course, most young people recoil at the thought of going back home and living under the watchful eyes of their parents. But subconsciously, many boomerang kids know home is comfortable turf where they can manipulate their parents. Before long, Mom and Dad are housing and feeding them, and doing their laundry as well.

Not a bad deal! And there are enough of their friends in the same situation that there is hardly any stigma attached to living with the Old Man and the Old Lady any longer.

Sometimes parents, or one parent, are thrilled that Johnny or Jane is back home. But often the other parent wants the kid out as soon as possible. This, and the clash of lifestyles between generations, is a recipe for family tension.

And things get worse when so-called adolescent adults stay and stay and stay for years on end, until they're not adolescents at all any more.