Re: "Another factor is discrimination, or unconscious bias, where “men and women are doing exactly the same job, but women are just valued lower,” Prof. Kaplan said"

If cut-throat competitive companies get away with paying women less for the same work, why don't they fire all the men and hire women in their place and beat their competitors?

See the real reasons the wage gap hasn't closed after thousands of measures over many decades:

"Salary Secrecy — Discrimination Against Women?" http://malemattersusa.wordpress.com/2014/10/27/salary-secrecy-discrimination-against-women/