The New York Times explores social science research about a new stage of life: emerging adulthood.

[A] growing body of research shows that the real Peter Pans are not the boomers, but the generations that have followed. For many, by choice or circumstance, independence no longer begins at 21.

Young people in the U.S., it seems, are taking their time reaching the traditional milestones of adulthood:

People between 20 and 34 are taking longer to finish their educations, establish themselves in careers, marry, have children and become financially independent, said Frank F. Furstenberg, who leads the MacArthur Foundation Research Network on Transitions to Adulthood, a team of scholars who have been studying this transformation.

“A new period of life is emerging in which young people are no longer adolescents but not yet adults,” Mr. Furstenberg said.

National surveys reveal that an overwhelming majority of Americans, including younger adults, agree that between 20 and 22, people should be finished with school, working and living on their own. But in practice many people in their 20s and early 30s have not yet reached these traditional milestones.

Marriage and parenthood — once seen as prerequisites for adulthood — are now viewed more as lifestyle choices, according to a new report released by Princeton University and the Brookings Institution.

One component of this shift is that young people are relying on their parents longer than previous generations. While parents used to invest most in their kids during the teen years, parental support now continues into the 20s.

In the late 1990s, however, parents’ spending patterns began to shift so that the flow of money was greatest when their children were either very young or in their mid-20s.”

More people in their 20s are also living with their parents. About one-fourth of 25-year-old white men lived at home in 2007 — before the latest recession — compared with one-fifth in 2000 and less than one-eighth in 1970.

The sizable contribution from parents not only strains already stressed middle-class and poor families, researchers argue, but could also affect institutions that have traditionally supported young adults in this period, like nonresidential and community colleges and national service programs.

Some young people are not just delaying milestones, but are redefining what it means to be an adult:

For many, marriage has disappeared as a definition of traditional adulthood, as more and more younger people live together. Today 40 percent of births are to unmarried mothers, an increase from 28 percent in 1990.

At the same time, more women are remaining childless, either by choice or circumstance. Twenty percent of women in their 40s do not have children, Mr. Furstenberg said, pointing out that “not having children would have been considered bizarre or tragic in the ’50s; now it’s a lifestyle choice.”