Let's see, I started with $25,000 5 1/2 yeras ago and here are the results

not to brag.....well, kinda bragging)
1998 (5 months) $20,000
1999 $414,000
2000 $1,657,000
2001 $1,016,000
2002 $525,000
2003 $ 165,000
Looks like I'm on the downside of the curve!
The point is that i think the question is misguided.
All one can do is trade safely. I went from maybe 1000% in a year , to 10%. You can't keep increasing at an exponential rate because increasing size will affect the market prices in a negative way, at least in many stocks.
As an example, I bought 25,000 ONE on theopening yesterday. The total opening was 75,000 shares. So, had I done 50,000, the price surely would not have been the same (it was a market order)
Just find a strategy that works and don't worry abt %'s.