Children raised within marriage do better on average. Why?

Does marriage lead to good or successful parenting, or are people with the traits of good parents more likely to marry?

Plenty of research shows that children who are raised by their married, biological parents tend to be healthier (both mentally and physically) and do better in school, than children who are not raised within marriage. But why?

Is the reason that married couples tend to have more resources, both financially and otherwise? That they can run a household more efficiently by specializing in different tasks and coordinating their efforts? That together they have a larger social network to rely on for support when things get tough? In short, what are the mechanisms through which marriage operates to enhance children’s wellbeing?

“The advantages of marriage for children’s wellbeing will be hard to replicate through policies other than those that bolster marriage itself.”

And beyond these mechanisms, is there something intrinsic to marriage itself that directly leads to better outcomes for children? At a time when so many American children are growing up with single or cohabiting parents, that’s an important question. What’s the best way to help all children thrive? Is it through policies that will help unmarried parents and families take advantage of the same mechanisms that married parents enjoy and thereby help their children have better life outcomes? Or through policies that encourage parents to get married and stay married?

When we look at the relationship between marriage and children’s wellbeing, the question of causality looms large. If children of married parents receive better parenting, for example, does that mean that marriage leads to good or successful parenting, or does it mean that people with the traits of good parents are more likely to marry?

Researchers call this a selection problem; that is, it’s possible that married parents tend to select marriage because they have certain qualities—higher incomes, more education, larger social networks—that also tend to produce better outcomes for children. Sophisticated statistical techniques can help sort out this problem. Though I won’t go into the technical details, researchers have used such techniques to examine the mechanisms through which marriage might improve children’s lives, looking for causal effects.

For a recent issue of the Future of Children, I reviewed research on a variety of mechanisms that might explain why children of married parents fare better than other children. Some of the mechanisms have been well studied, including parents’ income, fathers’ involvement with their children, parents’ physical and mental health, parenting quality, health insurance, home ownership, parents’ relationships, and family stability. Others have received less attention, including net wealth, constraints on borrowing, and informal insurance through social networks.

All of these mechanisms tend to vary by family structure (that is, whether the children have married parents or live in another family arrangement). All of them may affect some aspect of children’s wellbeing, such as health or educational attainment. Yet when researchers study them, they typically find that a given mechanism explains some but not all of the relationship between family structure and children’s outcomes.

For example, a recent study hypothesized that higher household income and greater access to health insurance might explain why children of married parents generally have better health than other children. The authors confirmed that family structure was associated with income and insurance, and that income and insurance were in turn associated with children’s health; however, even among children with similar household income and similar access to health insurance, those whose parents were married were also healthier. Thus, although the researchers found support for their hypothesis that differences in income and insurance produced differences in children’s health, they also found that family structure had other associations with health beyond income and insurance. This pattern of partial explanation is repeated across many, many studies.

The principal exception to this pattern comes from studies of family stability. When researchers measure instability by the simple number of transitions between different family arrangements (for example, from living with married to parents to living with a single parent after a divorce to living in a stepfamily), they find that instability often accounts for most if not all of the associations between family structure and children’s outcomes. So stability could be the mechanism through which marriage improves children’s wellbeing. Still, it could also be that these studies haven’t really explained why family structure matters; rather, they may have just found that counting the number of transitions is the best way to measure family structure.

What can we conclude from the fact that almost wherever we look, mechanisms such as higher income, more education, better access to health insurance and so on don’t fully explain the association between American children’s wellbeing and marriage? One reasonable conclusion is that the advantages of marriage for children’s wellbeing will be hard to replicate through policies other than those that bolster marriage itself. While helping unmarried parents increase their incomes, spend more time with their kids, find better child care, etc., would surely benefit children, these are likely to be, at best, only partial substitutes for marriage itself. The advantages of marriage for children appear to be the sum of many, many parts.