Where are women paid half what a man doing the same work earns? Any rational employer would fire all the men and use an all-woman workforce if he could swing that, but then there’d be no basis for comparison.

Competition in the marketplace ensures that wage differentials get closed up unless there’s a real difference in the work. Things that sometimes get discounted are the premium that employers must pay for dangerous work, odd hours, night shifts, etc.

My daughter could give you an earful about why she’s not actually underpaid, because she prefers the sane lifestyle that attends a few percent less dollars.