OVER the past 40 years, the geography of family life has been destabilized by two powerful forces pulling in opposite directions and occasionally scraping against each other, much like tectonic plates. One is the striking progress toward equality between men and women. The other is the equally striking growth of socioeconomic inequality and insecurity.

Since the 1970s, families have become more egalitarian in their internal relationships. But inequality among families has soared. Women have become more secure as their real wages and legal rights have increased. But families have become more insecure as their income and job instability have worsened.

Sometimes these trends counteract each other, with women’s work gains partly compensating for men’s losses in low-income families. Sometimes they reinforce each other, since the new trend for high-earning men to marry high-earning women increases the relative advantage of such couples over low-income or single-earner families. For all Americans, these trends have changed the rewards, risks and rules of marriage.

In 1977, two-thirds of Americans believed that the ideal family arrangement was for the husband to earn the money and the wife to stay home. By 2012, less than one-third still held this belief, according to a paper coming out this week by the Council on Contemporary Families.

Husbands have doubled the time they spend doing housework. One frequently cited study suggested that couples who shared housework equally had sex less frequently than couples who followed a more conventional division of labor. But a forthcoming study of more recent marriages finds that egalitarian couples report no difference in sexual frequency or satisfaction compared to couples who cling to traditional roles — the exception being the about 5 percent of marriages in which the husband performs most of the housework.

The researchers Christine R. Schwartz and Hongyun Han report[1] another striking indication of continuing progress toward marital equality. Through the 1980s, couples in which the wife had more education than her husband were more likely to divorce than couples in which the wife had less or equal education. But couples who have married since the early 1990s have no added divorce risk when the wife is better educated. In fact, the researchers found hints that such couples may now be less likely to divorce than those in which the husband has more education.

But while the sexes have become more equal, society as a whole has become far less, producing especially deep losses for young men. In 1969, by the time men reached age 25, three-quarters were earning wages that could support a family of four above the poverty line. By 2004, it took until age 30 for the same percentage of men to reach this income level. And while in 1969 only 10 percent of men ages 30 to 35 were still low earners, by 2004 almost a quarter of men in that age range remained low earners....