About half of all American children can expect to live with both of their biological parents at age fifteen, compared to two-thirds of children born in Sweden, Germany, and France, and nine-tenths of those born in Italy. This form of American exceptionalism reflects both higher rates of divorce and higher rates of breakup among cohabiting couples in the US. The increase in divorce, which began in the early 1960s but leveled off in the early 1980s, affected women at all educational levels. The increase in nonmarital childbearing, which was concentrated between the early 1960s and early 1990s, mainly affected non-white women and white women without college degrees. These changes appear to be a product of changes in sexual mores, which reduced the role of sexual attraction and increased the importance of economic calculations in decisions about whether to marry. The increased importance of economic factors coincided with a decline in non-college men’s ability to support a family and perhaps also with an increase in conflict over men and women’s roles.
Ellwood, David, and Christopher Jencks. "The Spread of Single-Parent Families in the United States since 1960." KSG Faculty Research Working Paper Series RWP04-008, February 2004.