Quote from mr19:
Not sure what would be in that database that would give me the answer. Even if that db had tick data AND trades/fills (which I have) it would be tough to estimate where you would have been filled.
Probably the best way to answer would be to running a significant number of shares in a live side by side comparison.
What I can tell from my trading (~ 500k shares/day) is that I do beat the NBBO spread on average BEFORE I give myself credit for rebates.
whats does "beating the spread" mean?