As someone that does try to incorporate bias into his analysis, IMO JB's summary couldn't possibly be more correct. IMO, it would be a huge mistake to try to incorporate bias into his figures for all the reasons he stated.

He does note the extremely dead rails. On those days you can look at the notes as to how wide the horse was. Then you can decide if you think a figure is a little suspect in terms of measuring the horse's actual performace.

However, all this stuff gets into very subjective evaluations of the horses' abilities going into a race vs. how they ran in the race and why. 10 fairly competent guys are going to have 20 different opinions.

So things like bias are going to have to remain a subjective area of the game. They can't be incorporated into a figure to the same degree of accuracy as time, ground lost and weight.