Is there any trader who attains annual 20% compounded after tax?
Raise your hand, please.
For sufficiently long time, one should make 1.2^20 = 38.3376 times for 20 years, and
1.2^50 = 9100.438 times from 30 to 80.
For example, with a seed of 10K (100K) at 30, he should have 9100*10K=91M (910M) at 80 to say annual 20% compounded.
PS) For him, there should be plenty of consistently-losing suckers (traders) in markets.
Before or after leverage?
The larger you get the more you run into liquidity issues rendering the supposed exponential growth of strategies a moot point. Big traders are essentially going to have fixed income.