If you spend any significant amount of time reading about the long-term decline of marriage among Americans with less education and lower incomes, you’ll notice a pattern: Liberals tend to blame the decline on labor-market forces, while conservatives tend to blame it on cultural and political factors.

The standard liberal view is that structural economic trends—automation, globalization, de-industrialization, de-unionization—weakened the earning potential of poor and working-class men, and thereby made them less “marriageable.”

The standard conservative view, by contrast, is that the sexual revolution, the feminist movement, and the rise of the modern welfare state discouraged marriage among the poor and working class by making it easier—both socially and financially—for women to have children without a husband.

Writing in the New York Times recently, Claire Cain Miller offered a balanced perspective:

In reality, economics and culture both play a role, and influence each other, social scientists say. When well-paying jobs became scarce for less educated men, they became less likely to marry. As a result, the culture changed: Marriage was no longer the norm, and out-of-wedlock childbirth was accepted. Even if jobs returned, an increase in marriage wouldn’t necessarily immediately follow.

Whether or not Miller is right about the initial causes of the marriage decline, she is surely correct that jobs alone will not be enough to repair the damage. Indeed, once cultural norms change—either for good or for ill—it’s very difficult to reverse things.

A positive example would be cigarette smoking. Between 1965 and 2015, the rate of smoking among U.S. adults dropped from around 42 percent to around 15 percent. Given how strongly the American public has turned against cigarettes, it’s virtually impossible to imagine that smoking rates will ever return to the levels that prevailed during the Mad Menera.

A negative example would be obesity. Since the early 1960s, the rate of adult obesity has climbed from about 13 percent to nearly 40 percent. Meanwhile, since the early 1970s, the rate of youth obesity has increased from about 5 percent to almost 19 percent. When we examine the dietary habits, lifestyle choices, and demographic characteristics of the U.S. population, it seems highly unlikely that the obesity epidemic will go away anytime soon.

As for the share of U.S. births taking place outside marriage, it went from 4 percent in 1950 to 41 percentin 2009, before dropping to just below 40 percent in 2016. The recent decline is of course welcome news. Still, the percentage of births to unmarried women was higher in 2016 than it was at any point in recorded history prior to 2007.

Patterns of nonmarital childbearing reveal major class divisions. According to a new report by Brad Wilcox and Wendy Wang of the Institute for Family Studies, nearly two-thirds (64 percent) of children born to poor mothers and more than one-third (36 percent) of children born to working-class mothers are born out of wedlock, compared with just 13 percent of children born to middle- and upper-class mothers.

Which brings us back to the marriage gap: Wilcox and Wang estimate that a majority (56 percent) of middle- and upper-class adults aged eighteen to fifty-five are married, versus only 39 percent of working-class adults and only 26 percent of poor adults.

“This stands in marked contrast to the 1970s,” they note, “when there were virtually no class divides in the share of adults married, and a majority of adults across the class spectrum were married.”

While Wilcox and Wang agree that economic pressures have played a role in undermining the marriage culture among less-educated Americans, they also make an important point about when these trends began:

The decline of marriage and rise of single parenthood in the late 1960s preceded the economic changes that undercut men’s wages and job stability in the 1970s. Shifts in the culture weakened marriage before shifts in the economy directly affected working-class families.

If policymakers want to help improve the marriage prospects of poor and working-class men, they could expand apprenticeships and vocational training, expand the Earned Income Tax Credit (EITC), reduce the burden of occupational-licensing requirements, increase public spending on infrastructure, or, as Wilcox and Wang suggest, soften or eliminate the marriage penalties in means-tested government programs (including the EITC).

Yet even if federal, state, and local officials did all of that, the impact on marriage rates would probably be minimal. That’s because, in 2017, class differences in family structure have relatively little to do with jobs, wages, or income. Instead, they mostly reflect cultural differences that developed over decades and cannot be erased by mere policy tweaks.

What we really need, as American Enterprise Institute scholar Charles Murray and others have emphasized, is a change in basic social attitudes. More specifically, we need greater numbers of poor and working-class Americans to embrace what Isabel Sawhill and Ron Haskins of the Brookings Institution have called “the success sequence”: Finish high school, work full time, and don’t have kids until after marriage.

To borrow from the late social scientist James Q. Wilson, the way to rebuild America’s marriage culture is “not from the top down by government policies, but from the bottom up by personal decisions.” If enough individuals chose to delay having children until they got married, the underlying culture would eventually change.

What about the claim that not enough poor and working-class men are “marriageable”? This argument seems too fatalistic. There’s no good reason that poor and working-class men can’t make the same family commitments as middle- and upper-class men, despite facing steeper economic challenges.

In fact, getting married can make it easier for poor and working-class men to overcome economic challenges and succeed in the labor force—not only because marriage can boost their household income, but also because it encourages positive behaviors. As University of Pennsylvania law professor Amy Wax has observed, “Marriage causes men to become more industrious, law-abiding, and sober.”

With all of that in mind, America’s political, civic, and cultural leaders should be far more aggressive about promoting the benefits of marriage, especially in underprivileged communities. Sawhill put it well on the twentieth anniversary of Dan Quayle’s famous Murphy Brown speech: “Unless the media, parents and other influential leaders celebrate marriage as the best environment for raising children, the new trend—bringing up baby alone—may be irreversible.”