Drill down, and learn the reason that women put in fewer paid hours: children and taking care of them. Compare the earnings of young women without children to those of men with similar education and skills - the women earn more.
You can argue that fathers should provide more child care. This argument runs head-on into the fact that 40% of children are born to unmarried women. Hymowitz notes:
All over the developed world women make up the large majority of the part-time workforce, and surveys suggest they want it that way.See her conclusion, which frankly isn't hopeful about the chances of a solution to wage disparity:
We don't know if there is a way to design workplaces so that women would work more or men would work less or both. What we do know is that no one, anywhere, has yet figured out how to do it.