In October 2011, University of Virginia's National Marriage Project reported that American kids are more likely to live with two biological, unmarried parents than one, single divorced parent [source: National Marriage Project]. Since the 1970s, the rate of couples shacking up without first walking down the aisle has swelled 14-fold, and as of February 2012, the majority of new mothers under 30 years old were unmarried [source: DeParle and Tavernise]. That doesn't, however, mean that romantic partners are out of the picture. A little more than 40 percent of kids under 12 years old share their homes with an unwed couple -- sometimes both biological parents, other times not; what worries some dual-parenting and marriage proponents is the risk that the trend toward unmarried cohabitation poses to children [source: Tavernise]. Without the legal rigors of marriage and divorce to contend with, it's logistically and financially easier for a cohabitating couple to call it quits, leaving kids in single-parenting situations.
But to other academics and experts, marriage has become overblown as a predictor of positive parenting. Peel apart the demographics of who is electing to get married these days, and it makes sense why married folks seem to do a better job bringing up baby. Specifically, Americans that go through with weddings tend to be older, more educated and wealthier than their cohabitating counterparts [source: Sassler]. Chances are, those economic and social attributes then trickle down beneficially to their children in ways that poorer, unmarried parents may not be able to replicate.
Regardless, the institution of marriage itself probably isn't an influential factor in child development; in sociological terms, predictors of success boil down to resources. By academic estimates, moms' and dads' incomes account for roughly 50 percent of adolescent outcomes, regardless of single or dual parenting statuses [source: Musick and Meier]. And considering that single parents -- only 40 percent of whom are employed full time -- are twice as likely to earn less per year than any other family structure, problematic trends in their children seem to be less the product of parenting gaps than economic resource gaps [source: Stanczyk].
Although data have demonstrated certain advantages to having more than one primary person involved in a child's upbringing, the numbers should also come with a caveat. As is often demonstrated by empirical data, most kids -- whether they're brought up by mothers, fathers, grandparents or guardians -- turn out just fine [source: Cowan and Cowan]. On top of that, there's a crucial metric that sociological studies can't boil down to empirical percentages for two-versus-one comparisons: the investment of parental love for a child. Good thing for families and kids of all sizes and structures that it's an equal-opportunity resource.