The only thing that’s curbed inequality has been catastrophe, Walter Scheidel notes:
Throughout history, only massive, violent shocks that upended the established order proved powerful enough to flatten disparities in income and wealth. They appeared in four different guises: mass-mobilization warfare, violent and transformative revolutions, state collapse, and catastrophic epidemics. Hundreds of millions perished in their wake, and by the time these crises had passed, the gap between rich and poor had shrunk.
But what of less murderous mechanisms of combating inequality? History offers little comfort. Land reform often foundered or was subverted by the propertied. Successful programs that managed to parcel out land to the poor and made sure they kept it owed much to the threat or exercise of violence, from Mexico during its revolution to postwar Japan, South Korea, and Taiwan. Just as with the financial crisis of 2008, macroeconomic downturns rarely hurt the rich for more than a few years. Democracy on its own does not consistently lower inequality. And while improving access to education can indeed narrow income gaps, it is striking to see that American wage premiums for the credentialed collapsed precisely during both world wars.