Profound changes have occurred in the structure of the human family over the past several decades in the United States and much of the Western industrialized world, These changes have altered drastically the contexts in which children are raised, and include significant increases in cohabitation, nonmarital fertility, and divorce (Bumpass, 1990; Sweet & Bumpass, 1987; J.Q.Wilson, 2002). About 30% of all children in the United States today-at least 20 million children-do not live with their genetic father, and one in two children born in the United States today will live in a single-parent household for some period of time before adulthood (U.S. Bureau of the Census, 2001; and see Bumpass & Sweet, 1989; Norton & Miller, 1992; J.Q.Wilson, 2002).