Regardless of their composition, families are generally regarded as a cornerstone of society. For many years, particularly when the United States was primarily an agricultural society, extended families—multiple generations living in the same household—were considered typical. As the culture became more urban and mobile, nuclear families—two parents and their children—became the American norm.

Shifts in economics, employment, moral values, and social conditions, however, have led to an increasing number of single men and women living alone, cohabitations without marriage, and single-parent families. A growing number of children, especially minorities, are being raised by only one parent or by neither parent, as is the case of those being raised by grandparents or foster parents. The role and the makeup of families, particularly minority families, have been undergoing change.

Marital Status

In March 2000 approximately 116 million Americans...