Johns Hopkins University researchers have found that waiting until marriage to have babies is now "unusual" among less-educated adults close to 30 years old.
"Clearly the role of marriage in fertility and family formation is now modest in early adulthood and the lofty place that marriage once held among the markers of adulthood is in serious question," sociologist Andrew J. Cherlin said.
"It is now unusual for non-college graduates who have children in their teens and 20s to have all of them within marriage," he said.
Among parents aged 26 to 31 who didn't graduate from college, 74 percent of the mothers and 70 percent of the fathers had at least one child outside of marriage, Cherlin found.
And, 81 percent of births reported by women and 87 percent of births reported by men had occurred to non-college graduates.
"If marriage retains its place anywhere," Cherlin said, "it would be among the college graduates, because most of them do not begin to have children until after they are married. The difference between them and the non-college-educated with regard to the percentage of births within marriage is so striking as to suggest a very different experience of early adulthood."
The researchers mined data from the National Longitudinal Survey of Youth, focusing on a sample of 9,000 "early adults" who reached ages 26 to 31 in 2011. They are the oldest members of the generation commonly known as millennials.
The study is detailed in "Changing Fertility Regimes and the Transition to Adulthood: Evidence from a Recent Cohort," a paper by Cherlin, Elizabeth Talbert and Suzumi Yasutake that was presented recently to the Population Association of America.
By that age, 53 percent of the women had given birth to at least one child and 64 percent of the mothers had at least one baby when they weren't married. (Forty-seven percent of the mothers had all of their babies out of wedlock.)
The percentage of unwed pregnancies goes up as the mothers' education level declines. The numbers are roughly the same for men.
Only 36 percent of the mothers had all of their babies while married-that's 46 percent of whites, 10 percent of blacks and 28 percent of Hispanics.
