Studies comparing the earnings of men and women have persistently found a pay differential that favors men. Since the World War II period there has been a dramatic increase in women's labor force participation rates, but these substantial gains have not been accompanied by improvements in their economic status comparable to men. Although the overall gap between the earnings of male and female full-time workers started to narrow in the late 1970s and 1980s, the differential remains large. Scholars have advanced supply side explanations for gender differences in occupations and earnings by focusing on the human capital model (Blau and Ferber, 1986). Supply side explanations focus on the observation that men and women enter the labor market with varied tastes and with different qualifications, such as education, formal training, and experience, or productivity-related characteristics. On the supply side, for example, men and women are unequally distributed across fields of study in college (Jacobs, 1994; Polachek, 1981) that have different average starting salaries. Consistent with that fact, Daymont and Andrisiani (1984) found that differences between the college major of men and women significantly contribute to the earnings gap. Within economics literature, the major supply side explanation for gender differentials in economic outcomes has been developed within the context of the human capital model. Economists such as Theodore Schultz (1960), Gary Becker (1975), and Jacob Mincer (1962) have pointed out that individuals and their families make analogous decisions regarding human capital investments. Resources are invested in an individual today in order to increase his or her future productivity and earnings. Examples of human capital investments include formal education, on-the-job training, job searches, and geographic migration. According to these human capital theorists, gender differences in these areas in both the amount and type of investment to make can produce sub-