Debates over modern American poverty tend to follow a familiar script: Liberals acknowledge the cultural factors but insist that the solutions are primarily economic, while conservatives acknowledge the economic factors but insist that the solutions are primarily cultural.

So it was not surprising when, at the recent “Conversation on Poverty” hosted by Georgetown University, President Obama suggested that a lack of government spending has contributed to a long-term decline in opportunity. Obama paid lip service to the issue of family breakdown, but he repeatedly implied that, since the 1980s, the biggest obstacle to serious poverty reduction has been America’s failure to make certain “common investments.”

“You look at state budgets, you look at city budgets, and you look at federal budgets,” Obama said, “and we don’t make those same common investments that we used to. And it’s had an impact. And we shouldn’t pretend that somehow we have been making those same investments. We haven’t been. And there’s been a very specific ideological push not to make those investments.”

Now, on the one hand, I happen to agree with some of the president’s ideas for boosting upward mobility, especially his calls for expanding the Earned Income Tax Credit and promoting apprenticeships. On the other hand, it requires either ideological blinders or historical ignorance to argue that America’s opportunity gap is the result mainly of government stinginess.

Heritage Foundation scholars Robert Rector and Rachel Sheffield have calculated that, in the first five decades of the War on Poverty, which started in 1964, the United States spent more than $22 trillion on means-tested anti-poverty programs (and that was in addition to the trillions we spent on Social Security and Medicare). The impact of these programs has been decidedly mixed: While they have helped reduce material deprivation, they have also discouraged marriage and work, thereby contributing to the long-term rise in out-of-wedlock births, the long-term drop in labor-force participation among prime-working-age men, and the spread of an underclass culture.

As for education spending, President Obama should read journalist Paul Ciotti’s analysis of the so-called Kansas City experiment. Between the mid-1980s and the late 1990s, a judicially imposed desegregation plan led to a massive increase in funding for Kansas City’s public schools. The impact? Here’s Ciotti, writing in 1998:

Kansas City spent as much as $11,700 per pupil — more money per pupil, on a cost of living adjusted basis, than any other of the 280 largest districts in the country. The money bought higher teachers’ salaries, 15 new schools, and such amenities as an Olympic-sized swimming pool with an underwater viewing room, television and animation studios, a robotics lab, a 25-acre wildlife sanctuary, a zoo, a model United Nations with simultaneous translation capability, and field trips to Mexico and Senegal. The student-teacher ratio was 12 or 13 to 1, the lowest of any major school district in the country.

The results were dismal. Test scores did not rise; the black-white gap did not diminish; and there was less, not greater, integration.

To locate the real sources of America’s opportunity gap, we need to look beyond government spending and focus on marriage — or, rather, the collapse of marriage in so many American communities.

In 2001, journalist Jonathan Rauch noticed that marriage was “displacing both income and race as the great class divide of the new century.” Eleven years later, Jason DeParle of the New York Times confirmed that “motherhood outside marriage now varies by class about as much as it does by race.” According to a report from the National Marriage Project and the Institute for American Values, the share of births occurring outside marriage among America’s least-educated women increased from 33 percent in 1982 to 54 percent in 2006–08, while the share among moderately educated women swelled from 13 percent to 44 percent. By contrast, the share among highly educated women remained very low, rising from 2 percent to just 6 percent.

The decline in marriage among Americans with lower levels of education is inextricably linked to the problems of entrenched poverty and social immobility. In 2013, the official Census Bureau poverty rate among married-couple families (5.8 percent) was 48 percent lower than the rate among all families (11.2 percent). If we look exclusively at families with children under the age of 18, the gap was even bigger: Married-couple families with children had a poverty rate (7.6 percent) that was 55 percent lower than the rate among all families with children (16.9 percent), and a staggering 81 percent lower than the rate among female-headed families with children and no husband present (39.6 percent).

The benefits of marriage transcend race and ethnicity. In 2013, the official poverty rate among black married-couple families with children (12.4 percent) was 61 percent lower than the rate among non-Hispanic-white female-headed families with children and no husband present (31.6 percent). It was also 27 percent lower than the rate among all families (married and unmarried) with children.

As I have explained many times before, the Census poverty rate is a deeply flawed indicator of American living standards. Yet it nevertheless highlights the crucial linkage between marriage and mobility. For that matter, a 2014 study by economists from Harvard and UC-Berkeley concluded that, if we compare demographic and geographic variations in mobility across the United States, “the strongest predictors of upward mobility are measures of family structure such as the fraction of single parents in the area.”

That is not surprising, given all the financial, emotional, and psychological support that marriage provides both for children and for their parents. As University of Pennsylvania law professor Amy Wax has written: “Marriage and strong families generate and preserve wealth, fostering the creation of small businesses. Marriage causes men to become more industrious, law-abiding, and sober. The traditional family is a mainstay of care for the old and infirm.”

By the same token, when two-parent married-couple families become virtually nonexistent in a given neighborhood, the result can be catastrophic social breakdown. A few weeks ago I quoted Daniel Patrick Moynihan’s prescient commentsfollowing the 1965 Watts riots: “From the wild Irish slums of the 19th-century Eastern seaboard, to the riot-torn suburbs of Los Angeles, there is one unmistakable lesson in American history: a community that allows large numbers of young men to grow up in broken families, dominated by women, never acquiring any stable relationship to male authority, never acquiring any set of rational expectations about the future — that community asks for and gets chaos. Crime, violence, unrest, disorder . . . are not only to be expected, they are very near to inevitable.”

In short: If we want to reestablish the cultural underpinnings of prosperity in lower-income communities, we will have to start rebuilding the marriage culture. No “conversation on poverty” is complete unless it acknowledges that simple reality.