The once dominant married couple family—a husband who works for pay, a wife who tends to home and children—has relinquished its privileged position, having now become a minority of all households.

More Americans are unmarried now than ever.

People marry later in life and sometimes not at all. And among those who do marry, the wife is more likely than ever to earn more or be better educated than her husband.

While these developments are society-wide, they were apparent earliest, and are now most pronounced, among African Americans. More than 2 out of every 3 black women, and a majority of black men, are unmarried.

More than half of college educated black wives have husbands who did not go to college. Many of these college educated wives will no doubt earn substantially more than their husbands.

African Americans are at the leading edge of changing patterns of family and gender roles.

Underlying the shifting terrain of intimacy are some welcome changes.

In earlier eras, it was hard to make it without being married. Through the middle decades of the 20th century, men married to gain a homemaker, and women for economic support. Spouses needed each other in the most practical of ways. In agrarian times, marriage brought the partner to help work the farm and manage the children, enterprises that no one could handle alone.

Now, it is more possible than ever to lead one’s life outside the bounds of marriage. Making a living, having sex, rearing children, setting up a household with a partner—none of that requires marriage.

As women have excelled educationally and, in turn, professionally, they have felt less need to look to marriage as a source of economic support.

Women are a majority of college graduates now, and consequently are poised to surpass men economically.

Among African Americans, nearly twice as many women as men graduate from college. As a result, women enjoy an unprecedented freedom to structure their lives as they choose, to marry only when they desire, or not at all.

Couples need no longer conform to rigid gender roles that have ceased to reflect how they want to structure their lives.

For all the benefits of personal freedom, if the experience of African Americans is any guide, then the marriage decline imposes costs as well.

These costs fall most harshly on children. Roughly 40% of children in the United States are born to unmarried parents. Among African Americans the percentage is higher still: 70%.

Whites now have children without being married at rates—25% overall, 60% for women who have their first child in their early 20s—that seemed unimaginable half a century ago, when so-called "illegitimacy" was viewed as a problem that would remain confined to African Americans.

While the increasing economic dominance of wives stems in part from women’s hard earned (and socially desirable) professional advancement, it also reflects a less salutary development: that many men have fallen behind educationally at the same time that the job prospects for blue collar workers have diminished, a casualty of technological change and the global labor market.

Again, African Americans provides the starkest expression of a broader phenomenon. Roughly half of all black boys drop out of high school. Confronted with few legitimate options for work, two out of every three of those dropouts go to prison, often for drug trafficking related offenses.

The struggles of so many black men leaves black women with too few potential partners. That’s a big part of why black women are so much more likely than their white counterparts never to marry.

Even women who are content with being single might prefer to marry, if only they could find the type of partner they want.

Those black couples who do marry are, I suspect, more likely than their white counterparts to be mismatched, to be partnered with someone who is not the best partner for them, in part due to the educational and economic chasm that often separates black spouses.

While relationships in which wives earn more than their husbands are a welcome change from the patriarchal model of past decades, they also confront distinct challenges, as couples struggle to adjust their expectations in light of the changing economic positions of husbands and wives.

As relaxed as gender roles have become—most wives now work, and increasing numbers of men participate in caring for children—one longstanding expectation remains widespread: that a husband contribute substantially to the economic support of his family.

When a wife supports the family because a husband cannot, problems often arise. Some husbands will feel insecure about not fulfilling the man’s traditional role; others will feel vulnerable to the criticisms of others.

Women play a role in these problems as well. Even as many women’s economic position has shifted from secondary to primary earner, few women feel that it is their responsibility to support their spouse.

Whereas men work to fulfill an obligation to provide for their family, including their spouse, many women work for a different reason: for self-fulfillment and so that they never become dependent on a man.

Many women thus view their earnings not as a contribution to the family pot that they share freely with their spouse, so much as, well, their money. If these women provide for their spouse, it is, they feel, because they want to, not because they have to.

However justifiable that attitude, it can only reinforce the anxieties of men who might already feel a bit insecure.

Educational and professional gaps between spouses create another problem: that of cultural difference. However much Americans might want to believe that we are all middle class, the reality is that class differences pervade our nation.

Education is both a reflection and a mechanism of the class divide.

A women, for example, who has been to college, embarked upon a career, and travels widely may not share the sensibilities or interests of a man who completed his education with high school and then took a job that doesn’t much broaden his horizons. These individuals may make a good life partner, just maybe not for each other.

The gender imbalance leads to another problem as well. Here’s an irony: the more some men fail, the more power other men gain.

As much as relationships embody love and care, they also form within a market. The scarcer desirable men become in that market, the more power they wield.

The relative power with which men and women enter a relationship depends partly on the options they have outside of the relationship. Whoever has more options outside of the relationship will have more power within it. The power imbalance inclines some of the most desirable men not to marry, or at the very least to be in no rush to do so.

Again, this is most apparent among African Americans; even black men who earn six figures are less likely than their white counterparts to marry.

These problems are less severe among white Americans largely because white men are not nearly as disadvantaged as black men. But just as the childbearing, work, and relationship patterns of white women have followed those of their black counterparts, the situation of white men may in the years ahead come to resemble more that of black men.

The trends are certainly moving in the same direction. Among whites as well, more women than men now graduate from college. And less educated white men who work in labor intensive fields confront the same labor market shifts that have made life difficult for so many black men, the demise of the well-paying manufacturing and industrial jobs on which earlier generations of men relied.

People no longer have to marry, but most still want to do so. Whether they will, and find the happiness they seek, depends not only one women’s freedom to choose the partner that is best for them, but also on how many men are able to be the sort of husband that women desire.

Ralph Richard Banks is the Jackson Eli Reynolds Professor of Law at Stanford Law School and the author of the new book, "Is Marriage for White People? How the African American Marriage Decline Affects Everyone