Rhapsodizing about the benefits of marriage may have a conservative air — promoting marriage among welfare recipients was a big deal during the George W. Bush administration — but you don’t have to be a conservative to bemoan these statistics.

It’s not only that those at higher education levels are far more likely to marry — they’re far more likely to marry each other. “Men used to marry their secretaries,” Sawhill observed. “Now they marry the woman they met in med school.”

As a result, Sawhill said, “These two-earner couples at the top are just making out like bandits and these single parents at the bottom have miserable lives. If the single parents were married, their life wouldn’t be so miserable. And at the top, if these high-earning professionals weren’t getting together and forming little collaboratives, they’d be worse off.”

About those collaboratives: More people are cohabiting these days, but as an economic matter, this doesn’t solve the problem.