Married workaholics both want to work—and, often, they do. Married women have nearly tripled their average workweek since the 1950s, absolutely crushing the working-hour growth of every other demographic...

The good news here is that women have the degrees, the means, and the freedom to work when they want to. The bad news is that the Typical American Family has only seen rising incomes in the last half century because of working wives.

In America today, a healthy, growing family income is a two-person job.

Just look what happens otherwise. The typical family with a stay-at-home wife/mom has seen incomes grow only 1 percent, after inflation, since 1980. But dual-earner households have seen a 29 percent raise, according to 2012 Census data.

The Single-Parent Trap

Working wives are the heroes of the Typical American Family in the last 50 years. The problem is that "typical" isn't quite so typical, anymore. Single moms or single dads, once rare, now lead 26 percent of all families, twice their share in 1950. This graph traces their ascent:

... and this graph traces their descent. Median incomes among families led by single dads and single moms have flat-lined or worse in the last few decades, falling behind those of married couples, whether or not the wife is working.

Single moms and single dads are more likely to be poor, not only because they don't have help in the household, but also because they didn't have much money to begin with.

In a strange twist, marriage has recently become a capstone for the privileged class. The decline of marriage, to the extent that we're seeing it, is happening almost exclusively among the poor. The lowest-earning men and women (i.e.: the least-educated men and women) have seen the steepest declines in marriage rates, according to the Hamilton Project.

The single parent crisis is concentrated among minorities. Single mothers and fathers, a rarity among white Americans, are common among minorities. More than 50 percent of Hispanic babies--and an astonishing 72 percent of black babies--are born to unwed mothers, according to Family Facts.

The causes of the single parent boom among minority populations is debatable. Sociologist William Julius Wilson pinned it on economics and crime, arguing that "high rates of [male] unemployment and incarceration meant that the local dating pool was populated by unmarriageable men." Another answer, from George A. Akerlof and Janet Yellen in a famous Brookings paper, suggested that abortion and contraception laws "[made] the birth of the child the physical choice of the mother [which made] marriage and child support a social choice of the father."

If the causes are mysterious, the outcome is not. The decline in marriage rates among poorer men and women robs parents of supplemental income, of work-life balance, and of time to prepare a child for school. Single-parenthood and inter-generational poverty feed each other. The marriage gap and the income gap amplify one another.