It's an interesting question, what (if anything) should be done to correct this, if this indeed makes up for the majority of gender wage disparities. Ex-Reddit CEO Ellen Pao got rid of wage negotiations altogether to correct for women's supposed inability to negotiate. That seems to me like the wrong way to go about it. I don't know the right answer, but I tend to favor bottom-up solutions (for example, encouraging people to learn negotiation and assertiveness strategies which are valuable for more than just making money) rather than protectionist top-down solutions (eliminating negotiations, affirmative action programs, encouraging litigious environments, etc).