That’s what Gerald Auten and David Splinter argue in a paper from last year.
… new estimates of top income shares using two consistent measures of income. Our measure of consistent market income includes full corporate profits and adjusts for changes from TRA86, including changes to the tax base and increased filing by dependent filers. In addition, we include employer paid payroll taxes and health insurance and adjust for falling marriage rates. The effect of these adjustments on estimated top income shares are dramatic. Using a consistent measure of market income shows that the increase in income shares of the top one percent since 1979 is about half of the PS unadjusted estimate. The increase since 1960 is about one-quarter of the unadjusted estimate. Moreover, our measure of broad income that includes government transfers reduces the top one percent share increase to one-tenth of the unadjusted estimate.
But in an NBER working paper, Annette Alstadsaeter, Niels Johannesen, and Gabriel Zucman argue that tax evasion and offshore wealth holdings work in the opposite direction:
Because offshore wealth is very concentrated at the top, accounting for it increases the top 0.01% wealth share substantially in Europe, even in countries that do not use tax havens extensively. It has considerable effects in Russia, where the vast majority of wealth at the top is held offshore. These results highlight the importance of looking beyond tax and survey data to study wealth accumulation among the very rich in a globalized world.