France Tried Soaking the Rich. It Didn’t Go Well.

In recent years, several prominent economists have brought attention to the problem of growing inequality. These scholars include Thomas Piketty, author of the best-selling book “Capital in the Twenty-First Century,” and Emmanuel Saez and Gabriel Zucman, who in a new book chronicle the rise in American wealth inequality. All three embrace the same solution: much higher taxes. Piketty has declared that billionaires should be taxed out of existence, and he called for a global wealth tax, while Saez and Zucman helped Democratic presidential candidate Elizabeth Warren design her proposal for a U.S. wealth tax. Piketty and Saez have also suggested taxing top incomes at a rate of more than 80%.

Other economists have struggled to evaluate dramatic proposals like this. Studies on the effects of taxation when rates are moderate might not be a good guide to what happens when rates are very high. Economic theories tend to make a host of simplifying assumptions that might break down under a very high-tax regime. Historical experience is of some help, because the U.S. had very high top income taxes in the 1950s, but economic conditions could be very different now.