"The 400 richest Americans — the top 0.00025 percent of the population — have tripled their share of the nation’s wealth since the early 1980s, according to a new working paper on wealth inequality by University of California at Berkeley economist Gabriel Zucman," the WashPost's Christopher Ingraham reports.

By the numbers: Those 400 Americans own more than the 150 million adults in the bottom 60% of the wealth distribution. According to the World Inequality Database maintained by Zucman and others, the bottom 60% saw their share of the nation’s wealth fall from 5.7% in 1987 to 2.1% in 2014. Zucman, who advised Elizabeth Warren on her wealth tax, finds that "U.S. wealth concentration seems to have returned to levels last seen during the Roaring Twenties."