The average effective tax rate stayed flat from 1945-2015, but the effective tax rate for the 0.1% and 1% fell during that time period. Bottoming out around the Bush years (although the graph only goes to 2015 so another source is needed to see how the Trump tax breaks have played out). The top for the 0.1% was almost 50% and the bottom was almost 20%. Now those almosts are working in the opposite directions so you should look at the graphs.

https://taxpolicycenter.org/taxvox/effective-income-tax-rate...

Now the 1% is paying more of the overall taxes, about 40%, but that number is also skewed (and can be misleading) by the absolute massive disparity between what the top and bottom make now. Plus of course reporting and tax compliance has changed a bit, plus a whole host of other confounding factors that this 40% statistic subsumes, but it's worth mentioning because it's always brought up in these discussions.