Quote from Ghost of Cutten:
The quick answer: risk an amount that will not bother you at all if you lose it...but no smaller than that.
Long answer: Position sizing should be determined by % win rate/loss rate, not by expectation or risk/reward ratio - since drawdown size is determined by amount risked * number of losses in a row (which is determined by % loss rate), not by profits or expectation (since a drawdown, by definition, has few or no winning trades in it). Here is the approximate formula:
High win rate (70%+): risk 2% of capital
Medium win rate (30-70%): risk 0.5% of capital
Low win rate (<30%): risk 0.1% of capital
This will insure modest drawdowns, and if you suck or make mistakes, which most traders do, then it will save you during times when you are off-form.
If you are an experienced and seriously profitable trader, then you can increase those positions sizes by 1.5-2 fold e.g. risk 3-4% on high win rate trades, rather than 2%. Just be aware that this will increase your risk substantially.
The only real exception I can think of is those trades that come along once every 2-3 years, with exceptional payoffs and high win rate e.g. the subprime housing trade, or stocks/credit in March 2009. In this case I think one could risk up to 5% of capital. However, this is an advanced move for expert traders, and most will do much better by sticking to the lower size limits.
Just caught up with the thread.
This is the best answer for me.
Thank you Ghost.
