From 1982 to 2018 the share of U.S. wealth held by the 400 richest Americans is estimated to have grown from 1% to around 3.5%, or probably around $3 trillion.
According to Emmanuel Saez and Gabriel Zucman, the University of
California at Berkeley economists who developed that estimate, that's in part because the wealthiest
American families declare only a small portion of their actual economic gains in any given year as income, while leaving the rest invested in stocks and other assets, to grow in value.
Saez, 48, has been involved in a series of what are considered groundbreaking studies of U.S. income, inequality and economic mobility that involved both developing techniques to impute income based on holdings of wealth, and extensive access to U.S. Internal Revenue records.