An analysis of contemporary data sets on gender and math ability finds that culture, not biology, is responsible for any gender gap in performance. The analysis appears in the Proceedings of the National Academy of Sciences and is based on a series of statistics, showing, for example, that girls at all grade levels now perform on a par with boys on standardized mathematics tests, that American girls are now taking calculus in high school at the same rate as boys, and that the percentage of U.S. doctorates in the mathematical sciences awarded to women has climbed to 30 percent, up from a nadir of 5 percent in the 1950s.