https://www.nytimes.com/2019/01/02/us/politics/bernie-sanders-campaign-sexism.html?emc=edit_na_20190102&nl=breaking-news&nlid=59668109ing-news&ref=cta/

Why were they paid less?

"Some former staff members said there was little pay transparency, and employees often negotiated their own salaries — practices that tend to favor men, who often feel more comfortable requesting higher compensation packages."

Men are sexist because they are better negotiators than women. Classic feminism: give women all the rewards (equal pay) and none of the responsibility (competitive negotiation skills)