This article discusses how and why related to a relatively undifferentiated family system in the United States in the middle of the last century changed to the current system of diverse family forms. The author suggests there is little doubt that we began to depart from the dominant model of the nuclear-family household in the late 1960s, and explains how change is a result of adaptation by individuals and family members to changing economic, demographic, technological, and cultural conditions. The author suggests that the breakdown of the gender-based division of labor was the prime mover.
Furstenberg, Frank F. (2014). Fifty years of family change from consensus to complexity. The Annals of the American Academy of Political and Social Science, 654, 12-30.