is it more accurate to calculate slippage as a percentage of the traded underlying or in absolute points? i am aware that many daytraders use absolute figures but i feel this is not really correct, since it distorts the picture. my argument is that people who use a percentage of their capital at any trade must reflect that when they calc their slippage as well. the absolute daily range of the sp future correlates by 0.79 with the future, whereas the daily range calculated as a percentage of the futures only correlates by 0.27 with the future. analysis since 1987. this does not mean more nor less than that the market is much more thinking in percentage terms than in absolute points. this means that whenever you use fixed points for a system you are overgearing in below average periods and overshooting in above average periods. the "mistake" is not that bad, since most daytraders cannot vary their investment to easily plus the timeframe over which they calculate their ranges are usually pretty short. my poit is that a slippage of 0.4 points on the emini means something different now than it did three months ago. anyone able to shed light on this? ps, sorry that this post is probably a tough read.