The Decline of Marrige in the Middle Class

Heritage  "In what he terms the “separate and unequal” state of marriage among socioeconomic classes, Wilcox found that middle-class Americans (those holding only a high school diploma) were much more likely to experience divorce and to have children out-of-wedlock than more highly educated citizens. While many Americans still hold a high regard for the institution of marriage, they are also increasingly tolerant of pre-marital sex, cohabitation, and non-marital childbearing. These attitudes are most prominent in the middle class, where the cultural battle for the health of marriage is raging."

… And Baby Makes Two   "Studies have found that children born to single mothers are vastly more likely to be poor, have behavioral and psychological problems, drop out of high school, and themselves go on to have out-of-wedlock children."
Slate