“You have already seen a reduction in economic inequality over the last few weeks because of the stock market, but there are potential longer-term effects for the 99 percent,” said Mr. Scheidel, who wrote “The Great Leveler: Violence and the History of Inequality From the Stone Age to the Twenty-First Century.”

“The poor will only be better off if it leads to policy change in an aggressive way,” he said.

Pandemics, Wars and Workers’ Rights

The Black Death — when the bubonic plague killed an estimated 30 percent to 60 percent of the European population in the mid-1300s — is an extreme example of how pandemics can rebalance societies.

Ultimately, it helped end serfdom in parts of Europe. Because so many people died, labor became scarce, and workers had more sway with landowning lords. Many peasants could, for the first time, own land or move for opportunities.

“It’s embedded in a larger series of economic shifts in Western Europe, but the economic impact of the Black Death is the thing you cannot possibly overstate, because it’s a shock to both the supply of labor and the demand,” Mr. Wyman said.

“If you’re a serf before the Black Death, you are in bad shape, you have no leverage — the lords can demand a lot from you,” he said. “After the Black Death, when the lord says, ‘Come plow my field,’ you don’t have to do that anymore.”

It appears the coronavirus pandemic will be nowhere near as deadly as the plague. But, he said, “even a relatively small-scale shock like this reopens the realm of the possible.”

Six centuries later, in the United States, a growing labor movement before World War I culminated, after the war, in stronger unions, widespread strikes and the end of the 12-hour workday. The war, in addition to the Spanish flu pandemic of 1918, resulted in a shortage of working men, so many of these jobs opened to women for the first time. In turn, women gained more power to argue for things like higher wages and the right to vote.