Grow up? Not so fast.

Michele, Ellen, Nathan, Corinne, Marcus and Jennie are friends. All of them live in Chicago. They go out three nights a week, sometimes more. Each of them has had several jobs since college; Ellen is on her 17th, counting internships, since 1996. They don’t own homes. They change apartments frequently. None of them are married, none have children. All of them are from 24 to 28 years old. Thirty years ago, people like Michele, Ellen, Nathan, Corinne, Marcus and Jennie didn’t exist, statistically speaking. Back then, the median age for an American woman to get married was 21. She had her first child at 22. Now it all takes longer. It’s 25 for the wedding and 25 for baby. It appears to take young people longer to graduate from college, settle into careers and buy their first homes. What are they waiting for? Who are these permanent adolescents, these twentysomething Peter Pans? And why can’t they grow up? Everybody knows a few of themfull-grown men and women who still live with their parents, who dress and talk and party as they did in their teens, hopping from job to job and date to date, having fun but seemingly going nowhere. Ten years ago, we might have called them Generation X, or slackers, but those labels don’t quite fit anymore. This isn’t just a trend, a temporary fad or a generational hiccup. This is a much larger phenomenon, of a different kind and a different order. Social scientists are starting to realize that a permanent shift has taken place in the way we live our lives. In the past, people moved from childhood to adolescence and from adolescence to adulthood, but today there is a new, intermediate phase along the way. The years from 18 until 25 and even beyond have become a distinct and separate life stage, a strange, transitional never-never land between adolescence and adulthood in which people stall for a few extra years, putting off the iron cage of adult responsibility that constantly threatens to crash down on them. They’re betwixt and between. You could call them twixters. Where did the twixters come from? And what’s taking them so long to get where they’re going? Some of the sociologists, psychologists and demographers who study this new life stage see it as a good thing. The twixters aren’t lazy, the argument goes, they’re reaping the fruit of decades of American affluence and social liberation. This new period is a chance for young people to savor the pleasures of irresponsibility, search their souls and choose their life paths. But more historically and economically minded scholars see it differently. They are worried that twixters aren’t growing up because they can’t. Those researchers fear that whatever cultural machinery used to turn kids into grownups has broken down, that society no longer provides young people with the moral backbone and the financial wherewithal to take their rightful places in the adult world. Could growing up be harder than it used to be? The sociologists, psychologists, economists and others who study this age group have many names for this new phase of life”youthhood,” ”adultescence”and they call people in their 20s ”kidults” and ”boomerang kids,” none of which have quite stuck. Terri Apter, a psychologist at the University of Cambridge in England and the author of The Myth of Maturity, calls them ”thresholders.” Apter became interested in the phenomenon in 1994, when she noticed her students struggling and flailing more than usual after college. Parents were baffled when their expensively educated, otherwise well-adjusted 23-year-old children wound up sobbing in their old bedrooms, paralyzed by indecision. ”Legally, they’re adults, but they’re on the threshold, the doorway to adulthood, and they’re not going through it,” Apter says. The percentage of