The rich and the very rich began increasing their income share after 1975
Here's a brief economic history of the last quarter-century in taxes and growth.If you want to read the actual study, here you go.
In 1990, President George H. W. Bush raised taxes, and GDP growth increased over the next five years. In 1993, President Bill Clinton raised the top marginal tax rate, and GDP growth increased over the next five years. In 2001 and 2003, President Bush cut taxes, and we faced a disappointing expansion followed by a Great Recession.
Does this story prove that raising taxes helps GDP? No. Does it prove that cutting taxes hurts GDP? No.
But it does suggest that there is a lot more to an economy than taxes, and that slashing taxes is not a guaranteed way to accelerate economic growth. More at Atlantic