The most incisive guide to issues facing the American family today . . . An invaluable resource for anyone wishing to stay on the cutting edge of research on family trends.

-W. Bradford Wilcox
Associate Professor of Sociology, University of Virginia 

Even After Childbirth, Marriage Delivers

Bryce J. Christensen and Robert W. Patterson

For decades, the empirical literature has confirmed that children raised by their married parents do significantly better, on average, than their peers reared by unwed or single parents. That verdict, however, has not persuaded all social scientists, some of whom claim the law of averages does not necessarily apply to those at the lower end of the income scale, particularly when parents marry after an out-of-wedlock birth. But in a dataset from the Fragile Families and Child Wellbeing Study, which represents exactly this subpopulation, two economists uncover new evidence that yes, parental marriage improves a child’s cognitive outcomes, even when that marriage occurs after the child’s birth.

Examining data on 958 children born between 1998 and 2000 to romantically involved but unmarried parents, Shirley Liu of the University of Miami and Frank Heiland of Baruch College investigated the effects of parental marriage after childbirth on child outcomes at age 3. While they found no evidence that parental marriage affects a child’s risk of developing asthma or behavior problems, the economists determined that parental marriage significantly increases a child’s cognitive development, as measured by the Peabody Picture Vocabulary Test.

The merit of the study is Liu and Heiland’s “potential outcome” methodology that accounts for parental self-selection into marriage, which allows a true comparison between children, according to the researchers, “who share similar parental background characteristics and assortative mating patterns who differ only in terms of whether their parents marry or not.” Consequently, the economic team estimates the effects of parental marriage after childbirth on child cognitive ability using a several ordinary-least squares (OLS) regressions as well as propensity-score matching estimates.

Out-of-wedlock children whose parents married scored 3.1 points higher on the Peabody test than did their peers whose parents failed to tie the knot. The effect was reduced to 2.2 points in OLS regressions that controlled for a full set of covariates, yet the correlation remained statistically significant (p<0.05). In the propensity-score matching analysis, the researchers found that parental marriage increased the child’s Peabody test scores between 3.5 and 4.4 points (a quarter of a standard deviation) over what those scores would have been had the same parents remained unmarried. Liu and Heiland also discovered that the effects of parental marriage on child development did not accrue to children when parents cohabited outside of marriage.

These enhanced scores for the children of parents who married may not seem significant. But according to the researchers, who used correlations from data from the National Longitudinal Survey of Youth as a baseline, a four-point increase in the Peabody test at age 3 “may raise the odds of high school graduation by 2 percentage points.”

Given what the economists deem are “particularly large gains from marriage,” what might encourage more unwed parents to marry? In their analysis, the researchers found that couples who “face a greater stigma of out-of-wedlock childrearing and those who are less similar in terms of their educational attainments are more likely to transition into marriage after childbirth.” The latter finding may surprise, yet it confirms that wedlock continues to facilitate—even among the low-income population where one spouse has less formal education than the other—specialization in home and market, allowing husband and wife to better allocate time and material resources to their children.

(Shirley H. Liu and Frank Heiland, “Should We Get Married? The Wedlock Effect of Parents’ Marriage on Out-of-Wedlock Children,” Economic Inquiry 50.1 [January 2012]: 17–38.)