(Photo: Leon Rafael/Shutterstock)

Earlier this month, the American Enterprise Institute and the Brookings Institution—two Washington, D.C.–based think tanks that typically occupy opposite ends of the ideological spectrum—released a joint report on poverty in America. The report, authored by an "ideologically balanced" working group of conservative, liberal, and centrist experts, lays out a comprehensive plan for fighting poverty that's admirable for its emphasis on evidence-based solutions from across the political spectrum.

The report recommends a variety of policies aimed at increasing the skills and wages of low-income workers, closing the education gap, and increasing economic mobility. But it's the section on family, particularly its emphasis on the declining institution of marriage and the perils of non-marital childbearing, that likely required particularly delicate negotiations between the working group's more liberal and conservative scholars. The authors' conclusion: Childbearing should be delayed until couples tie the knot, and marriage should be promoted as "the most reliable route to family stability and resources."

The biggest problem with this recommendation? It turns out that no one—liberal, conservative, or in between—has figured out how to convince unmarried parents to say "I do."

Non-marital childbearing has increased exponentially over the last 50 years. Over 40 percent of American children today are born to unmarried women; among African-American children, the number hovers above 70 percent. Many of these children are born to parents who live together, a type of parenting arrangement that, if stable and long-lasting, has the potential to offer the same benefits as marriage. But that's a big if; in the United States, these unions often are substantially less stable than marriage—cohabiting parents are three times as likely to break up by their child's fifth birthday than married parents.

This transformation of the American family has had significant and negative effects on low-income children. Research across the ideological spectrum clearly indicates that kids do best in stable, dual-parent households. Even after controlling for socioeconomic factors, studies show that children who grow up in single-parent households are poorer, less economically mobile, and more prone to a variety of behavioral issues than those raised by married parents.

No one—liberal, conservative, or in between—has figured out how to convince unmarried parents to say "I do."

While researchers on the left and the right have long debated how much of the "marriage" effect is actually the result of a selection effect—parents who choose to get married may be different in ways that researchers can't control for—it's clear the increase in non-marital childbearing has contributed to American poverty in a meaningful way.

Some of the benefits of marriage are obvious: Two pooled incomes go farther than one, and two sets of hands generally allow for higher-quality parenting. But a growing body of research suggests that the benefits extend beyond the simple arithmetic of an extra person or income in the house, and beyond even the individual: Recent research by a team of Harvard University economists indicates that family structure is the strongest predictor of economic mobility in a given neighborhood.

"When marriage is weak within a community, there are negative externalities that seem to flow from that," says W. Bradford Wilcox, a sociologist and director of the University of Virginia's Marriage Project. "So we know that crime is higher in communities with fewer married fathers, we know that parents are less involved in schools, we know that the ability is lower to support kids."

Conservatives have proposed marriage as a tool for fighting poverty before. Just last year, Jeb Bush, Paul Ryan, and Marco Rubio all gave speeches on this concept, arguing, in Bush's words, that a "loving family taking care of their children in a traditional marriage will create the chance to break out of poverty far better, far better than any of the government programs that we can create." But no one is exactly sure how to go about increasing marriage rates in the real world, particularly in the low-income communities that have so completely retreated from the institution.

Earlier this year, the Future of Children released a report on marriage and child well-being. In it, Ron Haskins, a Brookings Institution economist (and fierce marriage advocate) who participated in the poverty report, analyzed the effects of a variety of interventions that are frequently proposed when the question of increasing marriage rates comes up. He found no easy fixes to the problem of declining marriage rates.

So, for example, those marriage education programs piloted by the Bush administration in its Healthy Marriage Initiative? They were mostly a bust, with the exception of one program in Oklahoma.

"Generally speaking, [the research on marriage education programs] is not encouraging," Haskins says. "Having said that, the Oklahoma program did have at least short-term impacts. The recommendation would be to try to figure out why Oklahoma was effective."

Removing marriage disincentives from the U.S. tax code and the rules of means-tested welfare programs is another oft-proposed fix for the marriage problem. But while the tax code does hold some theoretical marriage penalties, Haskins' analysis concluded that those penalties don't apply to most low-income couples, many of whom would actually benefit from marriage, in the form of higher Earned Income Tax Credit earnings. Likewise, while means-tested welfare programs like TANF and SNAP do contain marriage disincentives, those penalties don't seem to actually dissuade people from getting married.

"For means-tested programs, it is the case that if you get married, your benefits could decline or you could lose them all together," Haskins says. "But the empirical case that it actually does reduce marriage among couples who get means-tested benefits is pretty weak."

Those marriage education programs piloted by the Bush administration in its Healthy Marriage Initiative? They were mostly a bust.

Perhaps mindful of this evidence, the scholars who authored the Brookings/AEI report don't lend their recommendation to either marriage education programs or changes to the tax code, calling instead for a public information campaign extolling the virtues of marriage, similar to past campaigns around smoking and teenage pregnancy.

"Major cultural norms have been changed many times before when leaders expressed firm and unequivocal views about even entrenched cultural attitudes, including norms surrounding civil rights and gay rights," write the report's authors. "Presidents, politicians, church leaders, newspaper columnists, business leaders, educators, and friends should all join in telling young people that raising kids jointly with the children's other parent is more likely to lead to positive outcomes than raising a child alone."

The Brookings/AEI report advocates another method of decreasing non-marital childbearing in the U.S., this one from the liberal side of the aisle: increasing access to family planning services.

"Everybody should be able to get on board with the idea that it's not a good idea to bring a child into the world accidentally," says Isabel Sawhill, a Brookings economist who has written extensively about the American family (Sawhill was not involved with the report). "Better family planning and more intended pregnancies and births would just be a win-win. They also would save the government a lot of money."

It's worth nothing that the report's many policies, though intended to increase the economic prospects of low-income men and women, may also serve to decrease non-marital childbearing, by making low-income men better "marriage material" and by increasing the opportunity costs of having a baby too early.

"It's no accident that working class and poor couples are the ones who are most likely to experience divorce, and are less likely to get married in the first place," Wilcox says. "I do think that's partly because there's an economic ... either calculus or concern, and when they have access to better-paying and more stable jobs, they feel more confident about going ahead and getting married in the first place. And in the second place, they're less likely to face those economic stresses that can tear apart a marriage."

Such an outcome, however, is not guaranteed. An article by sociologist Daniel Schneider that evaluated 16 programs designed to improve the economic well-being of participants found that, although many of the programs were successful in increasing the economic resources of disadvantaged men and women, only a few had any effect on marriage rates.

Despite the difficulties inherent in a large-scale effort to reverse a trend as deeply entrenched as the declining marriage rate, Wilcox thinks the consequences of not trying are worse than people realize.

"I don't have the magic bullet here, I don't think marriage is the magic bullet," Wilcox says. "But I think the left has to understand and realize that making peace with the retreat from marriage is also making peace with a world where millions of men have no real connection to family life and are not really in touch with their own children. And that has consequences for them, for the mothers of their children, for their kids, and also for their communities."