Studies of family structure have typically found that children raised in nuclear families—headed by the biological parents, a husband and wife who are married to each other—fare better in life than children raised in other types of families.  Children raised by both biological parents get on better across virtually the whole range of outcome measures.

This is a generally accepted finding.  The controversial issue has been whether the good outcomes are attributable to marriage itself or to other attendant circumstances.  Compared to single-parent families, nuclear families tend to have greater wealth, more stability of residence, and better social support.  Children in stepfamilies have usually experienced divorce and weakened relationship with a biological parent that nuclear-family children have not.  For these and other reasons, some commentators maintain that the real reason why children from non-nuclear families do worse is not marriage per se, but rather such factors as poverty, conflict, abandonment, and neglect.

Increasingly in recent years, children are being also being raised in cohabiting families—families in which a biological parent is living with, but not married to, a partner who is not a biological parent.  This has permitted more recent studies to focus on the effect of marriage itself.  By comparing the situations of children raised in cohabiting families with children raised in stepfamilies (headed by married couples, one of whom is not the biological parent), it is theoretically possible to attribute differences to marriage itself, after adjusting for other socio-demographic factors, such as parental age, education, income, etc.

A review article by Robin Fretwell Wilson of the University of Maryland School of Law looks at two 2003 studies that compared just such families.  The abstract of her article is posted here, and the full pdf text here.

The first study, by Wendy D. Manning and Kathleen A. Lamb, compared children living in married stepfamilies with children living in cohabiting families made up of the mother and her partner to whom she is not married.

The results are telling.  The study demonstrated a statistically significant difference in delinquency between children living with married parents, one of whom was a biological parent, and unmarried parents, one of whom was a biological parent. Teens in married stepfamilies were significantly less likely to be delinquent than teens living in unmarried, cohabiting households . . . Even after taking into account the parent's relationship with the child, family stability, and socioeconomic characteristics, this "marriage advantage"" continued to be significant . . . Importantly, this difference is similar in degree to differences the researchers also found between stepchildren and children in nuclear families.  [footnotes omitted]

Differences in delinquency by parental marital status persisted for children even after adjusting for socio-economic and other relevant factors.  Manning and Lamb concluded that remaining differences were attributable to marriage itself.

The second study, by Sandra L. Hofferth and Kermyt G. Anderson, took a different approach to the situation of children in different types of families.  They gathered data on fathers’ investment in the lives of their children.

Hofferth and Anderson compared investments by residential fathers in children in four different types of families: the nuclear family (married, biological parents), the cohabiting family (unmarried, biological parents), the stepfamily (married parents, one of whom is a nonbiological parent), and unmarried parents, one of whom is a nonbiological parent (mother cohabits with live-in partner).  Data came from 2531 children and their parents and examined father's weekly hours engaged with the child; weekly hours available to the child when the father was around but not actively participating in activities with the child; fathering motivation; number of activities the father participated in with the child in the past month; and "warmth" toward the child, as reported by fathers themselves. [footnotes omitted]

The researchers found that unmarried biological fathers invest less intensively in their children than do married biological fathers.

Unmarried biological fathers spent about four hours less a week on average with their biological children than married biological fathers, after controlling for race, father's age, child's gender and age, number of children, percentage of months lived with the father, father's work hours per week and earnings, and whether the father paid child support for children outside the house.  In fact, the data for unmarried cohabiting fathers looked more like stepfathers and mothers' partners than married biological fathers. [footnote omitted]

No significant differences were found with respect to hours available and number of activities per week, but for self-rated warmth, it was again found that unmarried biological fathers resembled stepfathers more closely than they did than married biological fathers.

The central insight Hofferth and Anderson derive from their research is this:

[M]arriage per se confers advantage in terms of father involvement above and beyond the characteristics of the fathers themselves, whereas biology does not. [footnote omitted]

These differences persist even after taking socio-economic status into account.  Given that children from less advantageous socio-economic backgrounds are more likely to be raised in cohabiting family settings, the effects of multiple disadvantages are often compounded.

Prof Wilson goes on to discuss possible explanations as to why marriage makes for better parents and so improves the lives of children.

Read the whole thing.

via MarriageDebate.com

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