“For thousands of years, civilization did not lend itself to peaceful equalization. Across a wide range of societies and different levels of development, stability favored economic inequality. This was as true of Pharaonic Egypt as it was of Victorian England, as true of the Roman Empire as of the United States. Violent shocks were of paramount importance in disrupting the established order, in compressing the distribution of income and wealth, in narrowing the gap between rich and poor. Throughout recorded history, the most powerful leveling invariably resulted from the most powerful shocks. Four different kinds of violent ruptures have flattened inequality: mass mobilization warfare, transformative revolution, state failure, and lethal pandemics. I call these the Four Horsemen of Leveling. Just like their biblical counterparts, they went forth to “take peace from the earth” and “kill with sword, and with hunger, and with death, and with the beasts of the earth.” Sometimes acting individually and sometimes in concert with one another, they produced outcomes that to contemporaries often seemed nothing short of apocalyptic. Hundreds of millions perished in their wake. And by the time the dust had settled, the gap between the haves and the have-nots had shrunk, sometimes dramatically.”