Researchers studying the factors behind out-of-wedlock births have found a significant variable that often is overlooked: child support. States that are strict in enforcing child support have up to 20 percent fewer unmarried births than states that are lax about getting unmarried dads to pay, the researchers found.

"The better the enforcement of child support, the more the cost of childbearing shifts from unmarried women to their partners," said lead author Robert Plotnick, a professor at the University of Washington's Evans School of Public Affairs. "This may make men more reluctant to become unwed fathers."

To document the link, Plotnick and three other social scientists teamed up to compare the toughness of each state's child support enforcement to the chances that women living in that state had out-of-wedlock births. Using a national sample of 5,195 women of childbearing age, they found a significant correlation between tougher enforcement and less chance of having unmarried births.

Since children of single parents run a higher risk of poverty and other social ills, policymakers have sought to stem the tide of unmarried births, only to see the rate rise from well under 10 percent of births in the 1960s to roughly a third of all U.S. births today.

Study co-author Irwin Garfinkel of Columbia University said most programs to discourage single parenthood " such as restrictions on welfare benefits " focus on the mothers.

"Decisions about sexual intercourse and marriage involve two people," Garfinkel said. "But research and policy debates have largely failed to recognize men's role in childbearing and how government policies may influence their behavior."

Plotnick, Garfinkel, and co-authors Sara McLanahan of Princeton University and Inhoe Ku of Seoul National University in South Korea theorized that forcing unmarried fathers to support their children financially might deter them from letting a pregnancy occur, or else motivate them to marry the mother if it did.

To test the theory, the researchers analyzed how well states do at identifying their unmarried dads and getting them to pay. Eight categories of child-support laws were tracked, covering everything from paternity testing to wage withholding. The researchers also measured the amount each state spent on child-support enforcement, divided by the number of single mothers. And to gauge the effectiveness of these measures, they calculated how the amount of child support collected compared to the amount that was owed.

The state-by-state measures of enforcement then got matched to national data on families from the Panel Study of Income Dynamics during 1980-93, the most recent period available.

The correlation between strictness of enforcement and rate of unmarried births was significant. Indeed, the results suggest that if every state had on its books at least six (out of a possible eight) child-support laws during the period, this would have cut the national rate of nonmarital childbearing by 17 percent.

Moreover, according to the results, if all 50 states had done at least as well in their enforcement efforts as the state ranked fifth from the top, that would have led to a 20 percent reduction in out-of-wedlock births.

"Any program that reduced out-of-wedlock childbearing by 17 to 20 percent," said Plotnick, "would be viewed as a major success."

While many states have continued to tighten up child support policies since the study's data were collected, even as recently as 2002 only one state (New Jersey) collected on at least 80 percent of its child support orders, according to Columbia University's National Center for Children in Poverty. Five states collected on fewer than four out of 10 such orders.

The main purposes of child support enforcement, of course, are to improve children's wellbeing and cut public welfare costs, but the researchers concluded that a reduction in unmarried births was an overlooked side benefit.

"Social policies sometimes have unintended bad side effects," Plotnick said, "so it's nice to see one that has positive impacts."

The paper is titled "The Impact of Child Support Enforcement Policy on Nonmarital Childbearing." The research was supported by the Center for Studies in Demography and Ecology at the University of Washington and a grant from the Institute for Research on Poverty at the University of Wisconsin-Madison.

Register for reporter access to contact details