Kay Hymowitz examines the gender gap statistics in City Journal and finds them all but entirely explained by career choices.
Of course, career choices may reflect some sexism in social norms, but that cuts both ways: in the legal profession, for example, it's entirely socially acceptable for the wife in a two-lawyer-income family to drop off of the BigLaw 80-hour-a-week track to pursue something more satisfying, but I know many fathers who feel trapped, and it's not clear that women don't have the better end of the deal in the resulting male-female disparity if the metric is happiness rather than income. (As the saying goes, law firm partnership is a pie-eating contest where the prize is more pie.) But the social norms causing the career choices causing the pay disparities are bottom-up, rather than top-down from employers, and can't be regulated away with even more burdensome litigation possibilities without doing severe damage to the economy and Constitution. Earlier.