St. Louis Fed study notes that different life choices between men and women lead to different wage outcomes.
Limor Golan, Andrés Hincapié, "Breaking Down the Gender Wage Gap by Age and by Hours Worked," The Regional Economist, October 12, 2016, accessed January 24, 2022
the gender gap when workers are 24 is substantially smaller than the gap when workers are in their mid-30s. This fact is well-known, and one of the main reasons for this pattern is that men and women make different choices over the life cycle. As they get older, women are more likely than men to work fewer hours outside the home and have breaks in their labor force participation (yielding less accumulated experience and possibly fewer labor market skills) and are less likely to hold highly compensated jobs with promotion prospects.