Is it true that there's a negative expectancy with slippage? If I place a market order, the odds of the market ticking up or down in between the time I place it and the fill should be equal right? Just wondering because it always seems to me that slippage goes against me rather than in my favor most of the time. If there is a negative expectancy, why? EDIT: Stop market orders might have a negative expectancy since it is ticking against you?