The American ideal of equality is based on the notion of equal moral worth, of an essential sameness among people (we are all semblables, in Tocqueville’s terms). The ideal retains some force, which is why aspiring politicians are so often obliged to adopt an “everyman” persona, stressing their similarity to ordinary Americans in terms of leisure pursuits, dress, and vocabulary. It is of course an exercise in false nostalgia to imagine that once upon a time everybody ate the same food, drank the same drinks, learned the same things in school, and raised their kids the same way. But differences seem greater today, and not just in terms of how people make their living, but how they live.

Class gaps in terms of parenting are not new, of course, but they are widening.

There is now, for example, no such thing as “The American Family.” The 1950s sitcom model of family life, as embodied in Leave it to Beaver, was always a semi-fiction; but it had a cultural pre-eminence that has now been entirely lost, giving way to a much more complicated kaleidoscope of family structures, including single parents, same-sex couples, childless (or “childfree”) couples, and cohabitating parents. With these changes, particularly the increase in single parenthood, has come a new problem: patterns of family formation are diverging along the same lines as income and education, accentuating inequality of opportunity. Isabel Sawhill has identified the source of the problem, noting in her forthcoming book, Generation Unbound: Drifting into Sex and Parenthood without Marriage, that “family formation is a new fault line in the American class structure.”

The proportion of children being raised by a single parent has more than doubled in the last four decades, and most of the growth rate is among those who are poorer and less educated. Unintended pregnancy rates are high. More parents have multiple relationships while raising their children, a trend the sociologist Andrew Cherlin describes as a “Marriage-go-Round.”

These differences in family formation patterns are reinforced by “assortative mating,” a stunningly unromantic term for the natural tendency of people to form relationships and have children with people like themselves. College grads marry college grads—and now there are of course many more female college grads around to marry. Online dating has just added algorithms to the process.

All this matters because family structure impacts on social mobility. Even the finest public school system in the world would be unable to compensate children for what Nobel laureate James Heckman calls the “biggest market failure of all”—choosing the wrong parents. Parents with college degrees have fewer children, later in life, and after marriage. And they are high-investment parents, spending generous amounts of time, energy, and money on their offspring. Class gaps in terms of parenting are not new, of course, but they are widening. In the 1970s, there were no serious differences in the amount of time spent with children by parents of differing education levels. Now there are significant disparities, which have come to be widely recognized thanks in large measure to the work of Robert Putnam (of Bowling Alone fame). There is also a gap in terms of how this time is spent—and it turns out that “quality” of time matters as well as quantity. Conversation is one example: children in the poorest families hear, on average, only 600 words per hour; those from the most affluent and highly educated families hear over 2,000 words per hour. By the age of 4, the total gap in words heard is estimated to be 30 million.

Bill Clinton frequently pointed out that parents raise children, not governments. But given that, as his wife Hillary Clinton correctly added, “it takes a village,” one might reasonably hope that once children enter school they will find something approximating a level playing field. This certainly looks to be a shared political goal. As George W. Bush, President Clinton’s successor, said in 2001, when launching the education reform initiative, No Child Left Behind: America’s “greatest challenge” (this was before 9/11) was to ensure that “every single child, regardless of where they live, how they’re raised, the income level of their family” would get a “a first-class education.”

But after decades of rhetoric and reform, the American education system is failing as an engine of social mobility. The poorest children (black and white alike) receive the worst public education. Achievement gaps between poor and affluent children tend to widen, rather than narrow, during the K-12 years.

Beyond the front porch and the school gates lies the community, which can also make or break life chances. The “social capital” generated by the networks and norms of community life can be crucial for upward mobility, especially for those from troubled homes: the coach who builds confidence, the neighbor who helps with a college application, the preacher who hears about a job opening, the family friend who keeps a struggling student from falling behind. But here, too, the gaps are widening. Community activism—volunteering, sports, neighbor support networks, church-going, and so on—is weak, and probably weakening, in less affluent neighborhoods.

These disadvantages typically compound each other, with low-income households, unstable families, and struggling parents living in the most hollowed-out communities, containing the worst schools, with the fewest social and institutional supports for those in need. So the barriers to upward mobility get even higher, along with the risks of getting stuck at the bottom of the ladder.

At a time when the United States is falling so far short of its own egalitarian ideal of Alger-style meritocracy, current economic and social trends are likely to make things worse. Piketty’s predictions, like all predictions, are far from proven; indeed, there are serious doubts about some of his assumptions. But if he turns out to be even fractionally right, we are in trouble. So, what is to be done? It hardly needs saying that there is no quick and easy fix. But there is also no excuse for sitting on our hands while the idea of opportunity becomes close to a cruel joke for so many. Opportunity is a public good, as well as a private one.

The good news is that U.S. politicians are waking up to the dangers of a divided nation. The bad news is that there is almost no consensus on which divides matter. Democrats emphasize inequalities in material dimensions, especially money; Republicans focus on class gaps in family, schooling, and community. Of course both are right. Cash gaps and class gaps both matter, and any political agenda that addresses only one side of the equality equation is destined to fail.

If we start with the money gap, Piketty’s proposed remedy, logically enough, is to levy heavier taxes on capital gains and wealth. This has been dismissed as a utopian, even un-American idea. Even now, when the desire to tax the rich could be expected to be at its zenith, Americans remain unenthusiastic redistributors. Indeed, an aversion to taxing inheritance is one of the few issues on which there is frequent bipartisan agreement. To Obama’s credit, he has tried to reverse the tide. To no avail. Even blue states like Maryland are reining back their estate taxes.

But this could change. There is actually a fairly deep anti-wealth seam in the American ideology of egalitarian individualism, as Piketty himself notes. Jefferson and Thomas Paine favored high taxes on estates to prevent the re-creation of an aristocracy. Even Andrew Carnegie, who loathed taxes in general, was a fan of the ones on inheritance: “I say the community fails in its duty, and our legislators fail in their duty, if they do not exact a tremendous share…” of the “enormous sum” bequeathed by the wealthy to their heirs. To this day, many wealthy Americans—Warren Buffett perhaps the most prominent and outspoken among them—continue to speak up against the unfairness of the tax system, and some, like Buffet and Bill Gates, have pledged to give away much of their fortunes rather than pass it on to their children.

Wealth inequality is a direct threat to a society that aspires to be ordered by merit and marked by social mobility. So proposals to tax the wealthy and use the revenues to fund opportunity-enhancing strategies are far from “un-American.” They are, in fact, quintessentially American. If the estate tax were returned to the level of the President George H.W. Bush years, for example, it would raise an additional $300 billion to $400 billion over the next decade—twice as much as we need to fund universal pre-K.

SOCIAL MOBILITY MEMOS Reeves is editor of and contributor to Social Mobility Memos, regular short pieces on the challenges of promoting greater social mobility and opportunity. Learn more >

There is a long way to go to persuade the American public of this, of course, but it is conceivable that with the right public framing, and consistent political pressure, opinion on wealth taxes could shift. The new investment income tax on couples with joint incomes of over $250,000 to fund Obama's Affordable Care Act provides a glimmer of hope that capital gains taxes are not completely off the table.

The social divide must also be addressed—with money, more creative thinking about how to help people acquire the skills they need, and institutional and financial support for those falling behind. Tackling the parenting gap, for example by expanding home visiting programs, ought to be a bipartisan cause. Likewise, action to even up quality in K-12 schools, with a concerted attack on “exclusionary zoning laws” that secure the borders of school catchment areas for the benefit of the affluent, more choice in schools for children of the lowest-income parents, and big financial incentives to attract the best teachers to the toughest schools.