I. Converging RolesOf the many advances in society and the economy in the last century, the converging roles of men and women are among the grandest. A narrowing has occurred between men and women in labor force participation, paid hours of work, hours of work at home, life-time labor force experience, occupations, college majors, and education, where there has been an overtaking by females.1 And there has also been convergence in earnings, on which this essay will focus. Although my evidence is for the United States, the themes developed here are more broadly applicable.1 See Goldin, Katz, and Kuziemko (2006) on women's college education. In terms of years of schooling, US women were ahead of men until the 1930s and then regained the lead (Goldin and Katz 2008a).

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The fraction of U.S. college graduate women entering professional programs increased substantially just after 1970, and the age at first marriage among all U.S. college graduate women began to soar around the same year. We explore the relationship between these two changes and the diffusion of the birth control pill ("the pill") among young, unmarried college graduate women. Although the pill was approved in 1960 by the Food and Drug Administration and spread rapidly among married women, it did not diffuse among young, single women until the late 1960s after state law changes reduced the age of majority and extended "mature minor" decisions. We present both descriptive time series and formal econometric evidence that exploit cross-state and cross-cohort variation in pill availability to young, unmarried women, establishing the "power of the pill" in lowering the costs of long-duration professional education for women and raising the age at first marriage.The careers of college graduate women and their age at first marriage both changed significantly in the United States with cohorts born around 1950. Women were 10 percent of first-year law students in 1970We have benefited from conversations and communications with Joshua Angrist, John Bound, Judith Chevalier, Edward Glaeser, Michael Kremer, David Laibson, David I. Levine, Steven Levitt, Rhona Mahony, Ellen Meara, Casey Mulligan, Alvin Roth, Kathryn Shaw, and Andrei Shleifer and from seminar participants at University of California at Berkeley, University of Chicago, Harvard, Massachusetts Institute of Technology, University of Michigan, NBER, Ohio State University, Uppsala University, and University of Wisconsin. John Donohue and Steven Levitt generously provided the abortion data. An earlier version was improved by the comments of two anonymous referees. For research assistance we thank Anne Berry and, especially, Tara Watson and acknowledge the Spencer Foundation in providing that funding.power of the pill 731 but were 36 percent in 1980. Among the cohort of female college graduates born in 1950, almost 50 percent married before age 23, but fewer than 30 percent did for those born in 1957. We ask whether the birth control pill and the legal environment that enabled young, unmarried women to obtain "the pill" altered women's career plans and their age at first marriage. Our answer is that they did.The pill directly lowered the costs of engaging in long-term career investments by giving women far greater certainty regarding the pregnancy consequences of sex. In the absence of an almost infallible contraceptive method, young women embarking on a lengthy professional education would have to pay the penalty of abstinence or cope with considerable uncertainty regarding pregnancy. 1 The pill had an indirect effect, as well, by reducing the marriage market cost to women who delayed marriage to pursue a career. With the advent of the pill, all individuals could delay marriage and not pay as large a penalty. The pill, by encouraging the delay of marriage, created a "t...

I thank Robert Barro for providing me with his educational attainment data, and Anne Hill for generously giving me her personal data files. Boris Simkovich and Linda Tuch served as very able research assistants on this project. The Brookings Institution provided funding for both my leave and the research assistance of Linda Tuck Lawrence Katz and t Paul Schultz provided valuable criticism and insights. This paper is part of NBER's research program in the Development of the American Economy. Any opinions expressed are those of the author and not those of the National Bureau of Economic Research.

for helpful comments. The views expressed herein are those of the author(s) and do not necessarily reflect the views of the National Bureau of Economic Research. NBER working papers are circulated for discussion and comment purposes. They have not been peerreviewed or been subject to the review by the NBER Board of Directors that accompanies official NBER publications.

Women are currently the majority of U.S. college students and of those receiving a bachelor's degree, but were 39 percent of undergraduates in 1960. We use three longitudinal data sets of high school graduates in 1957, 1972, and 1992 to understand the narrowing of the gender gap in college and its reversal. From 1972 to 1992 high school girls narrowed the gap with boys in math and science course taking and in achievement test scores. These variables, which we term the proximate determinants, can account for 30 to 60 percent of the relative increase in women's college completion rate. Behind these changes were several others: the future work expectations of young women increased greatly between 1968 and 1979 and the age at first marriage for college graduate women rose by 2.5 years in the 1970s, allowing them to be more serious students. The reversal of the college gender gap, rather than just its elimination, was due in part to the persistence of behavioral and developmental differences between males and females.

The careers of MBAs from a top US business school are studied to understand how career dynamics differ by gender. Although male and female MBAs have nearly identical earnings at the outset of their careers, their earnings soon diverge, with the male earnings advantage reaching almost 60 log points a decade after MBA completion. Three proximate factors account for the large and rising gender gap in earnings: differences in training prior to MBA graduation, differences in career interruptions, and differences in weekly hours. The greater career discontinuity and shorter work hours for female MBAs are largely associated with motherhood. (JEL J16, J22, J31, J44)

Current concern with relationships among particular technologies, capital, and the wage structure motivates this study of the origins of technology-skill complementarily in manufacturing.We offer evidence of the existence of technology-skill and capital-skill (relative) complementarities from 1909 to 1929, and suggest that they were associated with continuous-process and batch methods and the adoption of electric motors. Industries that used more capital per worker and a greater proportion of their horsepower in the form of purchased electricity employed relatively more educated blue-collar workers in 1940 and paid their blue-collar workers substantially more from 1909 to 1929. We also infer capital-skill complementarily using the wage-bill for non-production workers and find that the relationship was as large from 1909-19 as it has been recently. Finally, we link our findings to those on the high-school movement (1910 to 1940). The rapid increase in the supply of skills from 1910 to 1940 may have prevented rising inequality with technological change.