Bernie Sanders’ tax plan would impose annual tax rates of well over 100% on the richest 400 Americans, according to his economic advisers, mostly through his new wealth tax.

The idea that the federal government should take more from the very wealthy than they earn in a year is a policy innovation, one the Democratic candidate has advanced as part of a sweeping anti-inequality platform. Critics, however, argue that it’s unrealistic and would harm the economy by reversing billionaires’ incentives to innovate and invest.