Not only is birth control helping women not get preggers, it’s also making women richer. Widespread availability of oral contraception-a.k.a. ‘The Pill’-has played a major role in closing the gender wage gap since the 1980s, according to a new working paper from the National Bureau of Economic Research.

During the 1980s, the gap in median annual wages between women and men closed rapidly; women working full-time earned 60 percent of what their male counterparts earned in 1979, but earned 69 percent of men’s wages by 1989. There were a number of good reasons that gap narrowed so quickly-the women’s movement of the ’60s and ’70s, the increase in the number of women getting college degrees, and the protections afforded women by the 1964 Civil Rights Act and a series of legal decisions. But the researchers found that use of ‘The Pill’ accounted for 10 percent of the narrowing of the wage gap in the 1980s:

Its diffusion to younger, unmarried women improved their ability to time births, altered their expectations about future childbearing, and reduced the cost of altering career investments to reflect their changed expectations. The timing of its diffusion during the 1960s and 1970s also fits […]