Quote from ej420:
I think that a better way to ask my question might be "What sort of transaction costs do you factor in when backtesting intraday equities trading strategies?". Is it reasonable to assume average bid-ask spread + some flat commission? I also have some systems that execute fewer trades at half-hour time-frames or so, so that is also relevant there. I want to backtest in a realistic manner, and I am aware that the broker/links will have an effect on what 'realistic' is.
I'm sorry to respond to my thread so much. :eek:
bid-ask spread average + $0.0035/share is reasonable for back-testing...
Which is what you will pay on several million shares/month.
As you know...
The bid-ask spread varies a lot form $0.01-0.02 on liquid stocks...
To $0.05 to $0.10 or more on less liquid stocks.
A good trader exploiting a decent spread might have 50% of profits FROM the spread...
And 50% from quant analysis.
So the spread must be your friend and profit center.
If you are losing money on the spread...
Then you have no chance short-term trading.
Also..
Your profits margins are very important and should be at least 40-50%...
Because if your profits <<<< fees...
Then that will not likely sustain a business in the long run...
And your variance will be higher than optimal.
Also...
Back-testing has countless limitations.
You should be trading as soon and as much as possible...
Because it's the LOSSES that will move you up the learning curve... not the profits.