O ne of the most remarkable changes in labor markets since World War II is the rise in female participation in the workforce. In the United States, the employment rate of prime-age women has more than doubled from about 35 percent in 1945 to 77 percent at the end of the century, and similar trends are detected in the majority of OECD countries. These developments have generated a vast literature on the causes, characteristics, and consequences of the rise in women's involvement in the labor market. Existing work has indicated a number of supply-side explanations for these trends, including human capital investment, medical advances, technological progress in the household, and the availability of child care; and a recent line of research emphasizes the role of social norms regarding women's work in shaping the observed decline in gender inequalities.