Tax revenue as a percentage of GDP historically has floated around 18%

https://www.ceicdata.com/en/indicator/united-states/tax-reve...

Here's the income percentage held by the top 1% 1950-2010

http://piketty.pse.ens.fr/files/capital21c/en/Piketty2014Fig...

While its true that its higher now than it was the 1950s-1980s, its an increase of about 15%.

It if was the case that the very high marginal rates were actually being paid, you would expect the percentage of income held by the top 1% to be much higher.

Here's another source with more direct comparison - how much their income they actually paid in tax

https://taxfoundation.org/data/all/federal/taxes-on-the-rich...