The historian Walter Scheidel identifies “Four Horsemen of Leveling”: mass-mobilization warfare, transformative revolution, state collapse, and lethal pandemics. In addition to obliterating wealth (and, in the communist revolutions, the people who owned it), the four horsemen reduce inequality by killing large numbers of workers, driving up the wages of those who survive.

Steven Pinker, Enlightenment now: the case for reason, science, humanism, and progress, New York, 2018, p. 107