This is a backtest of an extremely simple strategy which I'll also try to attach to this post. It's long only, just holding a bigger position when SPY goes above a moving average, and going to cash when it goes below. It has positive (not necessarily good, just positive) returns. It also has a stop loss.
As soon as I turn on any commission or slippage, though, it gets absolutely destroyed and the only thing that remains consistent is losing money :)
I'm tracking the amount of trades, and it's 35000 in SPY trades in about 20 years, or about 7 trades per day. It trades a lot some days, even 100 times; other days it trades two times.
What's surprising to me is that I wouldn't think this amount of trading would make a profitable algorithm just consistently lose money. I thought this wouldn't be considered that many trades. I bet there are retail traders who have made a similar amount of trades!
So where's the big problem I'm overlooking? Is there some tool to analyze intraday algorithms, quantify the impacts of slippage and commissions and then optimize the algorithm to reduce them?