The study looked at how the number of hours worked each year affects how much money people earn in the U.S. from 1976 to 2019. They found that changes in how many hours women work each year have a big impact on the differences in how much money they make. This shows how women's work patterns have changed a lot over time. For men, changes in the number of hours they work mainly affect how much money lower-earning men make, and this is influenced by economic ups and downs.