Much of the wage gap can be explained away by simply taking account of college majors. Early childhood educators and social workers can expect to earn around $36,000 and $39,000, respectively. By contrast, petroleum engineering and metallurgy degrees promise median earnings of $120,000 and $80,000. Not many aspiring early childhood educators would change course once they learn they can earn more in metallurgy or mining. The sexes, taken as a group, are somewhat different. Women, far more than men, appear to be drawn to jobs in the caring professions; and men are more likely to turn up in people-free zones. In the pursuit of happiness, men and women appear to take different paths.

But here is the mystery. These and other differences in employment preferences and work-family choices have been widely studied in recent years and are now documented in a mountain of solid empirical research. By now the President and his staff must be aware that the wage gap statistic has been demolished. This is not the first time the Washington Post has alerted the White House to the error. Why continue to use it? One possibility is that they have been taken in by the apologetics of groups like the National Organization for Women and the American Association of University Women. In its 2007 Behind the Pay Gap report, the AAUW admits that most of the gap in earnings is explained by choices. But this admission is qualified: “Women’s personal choices are similarly fraught with inequities,” says the AAUW. It speaks of women being “pigeonholed” into “pink-collar” jobs in health and education. According to NOW, powerful sexist stereotypes “steer” women and men “toward different education, training, and career paths.”