The Washington Post reports,

As marriage with children becomes an exception rather than the norm, social scientists say it is also becoming the self-selected province of the college-educated and the affluent. The working class and the poor, meanwhile, increasingly steer away from marriage, while living together and bearing children out of wedlock.

Regarding marriage and income class, which is the cause and which is the effect? If you’re a bleeding-heart liberal, it is economic stress that leads to single-parenthood.

“The culture is shifting, and marriage has almost become a luxury item, one that only the well educated and well paid are interested in,” said Isabel V. Sawhill, an expert on marriage and a senior fellow at the Brookings Institution.

However, the example in the story seems to reflect causality running in the other direction.

When the Fitzhenrys married (he was 42, she was 32), it changed the way they managed their finances, which Jim said had been in a “death spiral” when they were single. Michelle quickly paid off $20,000 in credit-card debt. Jim cut up most of his credit cards and got rid of a BMW convertible.

Among its many benefits, marriage raises the earnings of men and motivates them to work more hours. It also reduces by two-thirds the likelihood that a family will live in poverty, researchers have learned.

Or, could there be a third factor that causes both marital stability and high income?

“Although we didn’t plan it that way and we certainly didn’t marry for money, it turned out that a byproduct of the values we both care about has been financial success,” said Michelle, who places the couple’s annual earnings between $350,000 and $400,000, much of which is invested conservatively.

I think that Michelle’s social science is probably better than that of either the liberal or conservative researchers. Start with the right set of values (or characteristics such as self-discipline and self-control), and you are more likely to end up like the Fitzhenrys.