Why would they claim that? Because surprise, surprise the conditional difference in means is smaller than the unconditional difference in means!
I sent this letter to the editor in. It has not been published at this point:
"Mark Perry and Andrew Biggs (April 7th, 2014, "The '77 Cents on the Dollar' Myth About Women's Pay") seem to confuse our ability to attribute the gender pay gap to various factors with the idea that the gap itself is a "myth". Far from demon...strating that the gap is "economically illogical", by highlighting the various determinants of pay disparities Perry and Biggs are actually confirming the existence of the gap and presenting evidence on where it originates.Mark Perry's next column: The black unemployment rate is a myth because if you control for unequal education, terrible treatment by the justice system, and differences in a family structure a whole lot of it seems to go away! Also must not be caused by discrimination.
Economists have been studying female labor market participation and performance for decades. This research does not stop at the question of pay disparities. We know, for example, that many occupations are highly segregated by gender, and that large gender disparities exist in the amount of time dedicated to household work. Young women may be nominally free to major in whatever they choose, as Perry and Biggs suggest, but these choices are heavily conditioned by earlier experiences in the home and in primary and secondary school.
All of these disparities are closely related to each other and to the pay gap, and they pose a real problem for those of us that value gender equity. Dismissing the gender pay disparity because it is deeply embedded with other disparities does not clarify the issue at all; it confuses the issue.
Doctoral student, American University Department of Economics
Specializing in labor economics and gender economics"
If anyone is interested in studying the economics of gender and the family, you should look into American University. It was the first U.S. university to have a field specialization in gender economics, it offers courses in both gender macro and micro, and a lot of the faculty are working on these issues.