New York Times:  Economic Inequality and the Changing Family, by Jason DeParle:

[T]he widening in many measures of inequality can be traced in part to changes in marriage patterns, rather than just changes in individual earnings. A number of scholars have looked at the varied dimensions of this thesis — growing inequality, changes in family structure, and the connection between the two. Here is a look at some of their findings….

An interesting pattern over the last four decades is that inequality has grown much faster for households with children than it has for households over all — an indication that changes in family structure (as opposed to wages and employment alone) have increased inequality.

Bruce Western and Tracey Shollenberger of the Harvard sociology department compared households at the 90th percentile and the 10th percentile. In 1970, the top households had 8.9 times the income of the bottom. By 2011 they had nearly 11.7 times as much — inequality between them grew 31%. But among households with children it grew 121%. (The ratio went from 4.8 in 1970 to 10.6 last year.)

Changes in family structure may explain anywhere from 15 to 40 percent of the increased inequality in recent decades.