Once women start doing a job, “It just doesn’t look like it’s as important to the bottom line or requires as much skill,” said Paula England, a sociology professor at New York University. “Gender bias sneaks into those decisions.”

She is a co-author of one of the most comprehensive studies of the phenomenon, using United States census data from 1950 to 2000, when the share of women increased in many jobs. The study, which she conducted with Asaf Levanon, of the University of Haifa in Israel, and Paul Allison of the University of Pennsylvania, found that when women moved into occupations in large numbers, those jobs began paying less even after controlling for education, work experience, skills, race and geography.

https://www.nytimes.com/2016/03/20/upshot/as-women-take-over...