Quote: High achievers will lose the incentive to increase their contribution, simply because if their efforts are successful and their income increases, much of their increased income will be taxed at a high rate, so they keep much less. That will reduce their incentive and slow economic growth.

There is absolutely NO truth to this statement and no verifiable data to prove it. The economy buzzed along just fine and grew under high progressive taxes for decades until the code began getting flattened under Reagan and subsequent administrations- corresponding (and perhaps causing ) the growth of the largest income disparity since the gilded age- the data is readily available

https://www.cbpp.org/income-gains-widely-shared-in-early-postwar-decades-but-not-since-then-3