"You have to ignore many variables to think women are paid less than men. California is happy to try."

Writes Sarah Ketterer in The Wall Street Journal in "The ‘Wage Gap’ Myth That Won’t Die" (which you can get to without subscribing if you Google some of the text).

 The Bureau of Labor Statistics (BLS) notes that its analysis of wages by gender does “not control for many factors that can be significant in explaining earnings differences.”

What factors?... Men are significantly more likely than women to work longer hours...

Career choice is another factor.... [W]omen flock to college majors that lead to lower-paying careers.... [O]f the 10 highest-paying majors... only one, “pharmacy sciences and administration,” is majority female. Eight of the remaining nine are more than 70% male.

If the pay were equalized, wouldn't that only exaggerate the sex difference in the career choices, with even fewer women motivated to go into computers and science? I doubt if men avoid low-paying majors like "drama and theater arts" and "counseling psychology" only because of the pay. But I'm not stating an opinion about whether it's bad that there are gendered differences in career choices. Maybe that's just fine, and it's a shame that women doing what they like includes lower pay. It's just one of the many factors you have to take into account when you want to do with your life (including whether you want to spend more time with your family). But for those who think there's a problem that there aren't enough women in the STEM fields, removing the economic incentive won't help.