Contrary to popular belief, it is not because employers pay women less than men for doing the same jobs. According to an article on the Economist, women earn 98% of the wages of men who are in the same roles at the same employers.
Women, however, outnumber men in lower-tier jobs, and they cluster in occupations and industries that pay lower salaries overall. In America, the four jobs done by the biggest numbers of women—teacher, nurse, secretary and health aide—are all at least 80% female.
A recent study estimated that in America women’s future wages fall, on average, by 4% per child, and by 10% per child in the case of the highest-earning, most skilled white women.
This pattern means that men get a better shot at a pay rise or a promotion than their female colleagues, and are less likely to be in jobs for which they are overqualified.