The article discusses the reversal of the college gender gap in the United States, where female college enrollments and graduation rates have increased relative to male rates since the 1970s. From 1900 to 1930, male and female college enrollments were nearly equal. However, male enrollments increased relative to female enrollments in the 1930s and after World War II, reaching a peak in 1947. Starting in the late 1960s, female college enrollment and graduation rates began to rise rapidly, driven by changing expectations of future labor force participation and increased access to higher education. By 1980, the college gender gap had reversed, with female enrollments and graduation rates approaching parity with males. This trend continued, with female college graduation rates surpassing male rates by 2003. The reversal of the gender gap in college attendance and graduation is attributed to several factors, including changes in high school preparation, such as higher achievement test scores and increased enrollment in math and science courses by girls. These changes were driven by increased economic returns to college for girls, which were influenced by improvements in labor market opportunities and delayed first marriage. Long-standing behavioral and developmental differences between boys and girls also contributed to the new college gender gap favoring females. The article uses longitudinal data from high school graduates in 1957, 1972, and 1992 to analyze the sources of the narrowing of the gender gap in college and its reversal. It finds that high school girls improved relative to boys in college preparation, as measured by achievement test scores and math and science course taking. The changes in these proximate determinants of college investments appear to be driven by increases in girls' expected economic returns to college, which in turn arose from improvements in perceived labor market opportunities and an increase in the age of first marriage. The article also discusses the role of family socioeconomic status in college outcomes, finding that the female advantage in college graduation rates has increased across all socioeconomic levels. The reversal of the gender gap in college attendance and graduation is also attributed to changing expectations of future labor force participation, the age at first marriage, and behavioral problems at young ages. These factors, combined with changes in social norms and legal protections for gender equality, have contributed to the current gender imbalance among college undergraduates in the United States and elsewhere.The article discusses the reversal of the college gender gap in the United States, where female college enrollments and graduation rates have increased relative to male rates since the 1970s. From 1900 to 1930, male and female college enrollments were nearly equal. However, male enrollments increased relative to female enrollments in the 1930s and after World War II, reaching a peak in 1947. Starting in the late 1960s, female college enrollment and graduation rates began to rise rapidly, driven by changing expectations of future labor force participation and increased access to higher education. By 1980, the college gender gap had reversed, with female enrollments and graduation rates approaching parity with males. This trend continued, with female college graduation rates surpassing male rates by 2003. The reversal of the gender gap in college attendance and graduation is attributed to several factors, including changes in high school preparation, such as higher achievement test scores and increased enrollment in math and science courses by girls. These changes were driven by increased economic returns to college for girls, which were influenced by improvements in labor market opportunities and delayed first marriage. Long-standing behavioral and developmental differences between boys and girls also contributed to the new college gender gap favoring females. The article uses longitudinal data from high school graduates in 1957, 1972, and 1992 to analyze the sources of the narrowing of the gender gap in college and its reversal. It finds that high school girls improved relative to boys in college preparation, as measured by achievement test scores and math and science course taking. The changes in these proximate determinants of college investments appear to be driven by increases in girls' expected economic returns to college, which in turn arose from improvements in perceived labor market opportunities and an increase in the age of first marriage. The article also discusses the role of family socioeconomic status in college outcomes, finding that the female advantage in college graduation rates has increased across all socioeconomic levels. The reversal of the gender gap in college attendance and graduation is also attributed to changing expectations of future labor force participation, the age at first marriage, and behavioral problems at young ages. These factors, combined with changes in social norms and legal protections for gender equality, have contributed to the current gender imbalance among college undergraduates in the United States and elsewhere.