"A new study from researchers at Cornell University found that the difference between the occupations and industries in which men and women work has recently become the single largest cause of the gender pay gap, accounting for more than half of it. In fact, another study shows, when women enter fields in greater numbers, pay declines — for the very same jobs that more men were doing before.
Consider the discrepancies in jobs requiring similar education and responsibility, or similar skills, but divided by gender. The median earnings of information technology managers (mostly men) are 27 percent higher than human resources managers (mostly women), according to Bureau of Labor Statistics data. At the other end of the wage spectrum, janitors (usually men) earn 22 percent more than maids and housecleaners (usually women).
The same thing happened when women in large numbers became designers (wages fell 34 percentage points), housekeepers (wages fell 21 percentage points) and biologists (wages fell 18 percentage points). The reverse was true when a job attracted more men. Computer programming, for instance, used to be a relatively menial role done by women. But when male programmers began to outnumber female ones, the job began paying more and gained prestige.
Citation for that specific assertion: https://www.researchgate.net/publication/37710729_Making_Technology_Masculine_Men_Women_and_Modern_Machines_in_America_1870-1945
