For those in Washington obsessed with reducing income inequality, the standard prescription involves raising taxes on the well-to-do, increasing the minimum wage, and generally expanding government benefits—the policies characterizing liberal, blue-state governance. If only America took a more "progressive" approach, the thinking goes, leaving behind conservative, red-state priorities like keeping taxes low and encouraging business, fairness would sprout across the land.

Among the problems with that view, one is particularly...