First, I don’t assume the track stays the same speed (see “Changing Track Speeds” in the Archives section). And I don’t assume that Lasix makes non bleeders faster. There’s supposed to be a big Lasix study in the works, in the unlikely event it’s done right we might find out more about that.

Basically, you makes figures off the horses that run well, or at least run a representative race. You don’t make them off the ones who run poorly, which is what happens when horses bleed (choke). As a practical matter if more run poorly you have less data points to work with, which makes getting it right trickier.