Marriage rates have shown short‐term and long‐term fluctuations over time. Particularly since the early 1980s, a decreasing pattern of marriage rates in most developed western societies seems to be emerging. Nevertheless, marriage still exerts an important influence in people's lives, particularly in less developed societies. This entry reviews some of the factors behind the decrease in marriage rates. It is suggested that women's educational levels and work opportunities, cultural factors, cohabitation, and imbalanced sex ratios have played a major role in the decline of marriage rates.

Single parenthood has been increasing within the developed world and it has been affecting traditional roles and changing relationships. Scholars have made efforts to understand the existing various types of single parenthood, as well as its causes and its consequences. The majority of single parents are women who are in charge of their children, but there are an increasing number of male parents. Desertion, widowhood, separation and divorce, or simply preferring to be alone have been pointed as potential causes. Single parenthood has often been associated with higher probability of unemployment and insufficient income, and also potentially affects the educational and socialization outcomes of children. Nonetheless, families and societies have found ways to adapt to these changes. Whether social policies address these issues adequately and how these policies are conceived are disputable matters.