Sunday, 3 May 2009

A Bogus Beyer

Mine That Bird got a Beyer of 105 for his upset win in the Derby. That's four less than Big Brown, five more than Giacomo. Is it enough to win the Preakness? Let's skip this question and concentrate on a more fundamental one: Why would you assume he ran a 105?

Determining a speed figure is a tricky and partially subjective task under any circumstances, and the certainty with which the DRF is advertising and comparing them may sell their paper, but is way overblown. The fact that BSF's can frequently be questionable, misleading or plain false is something Andy Beyer has acknowledged himself, although you wouldn't think so from the way he sometimes touts his system. But assessing one for a race like yesterday’s Derby comes down to an exercise in guesswork rather than science. Anybody who has ever looked up the process of determining a Beyer (basically by relating the times of the day’s card, or parts of the card, to expected times) should realize immediately that the Derby had to be practically rated against itself, with few clues provided.

Gaps between races on Derby Day were just short of one hour, and track maintenance was done between races, with officials specifically aiming to make the track faster. The last race before the Derby was on the turf, and the only other two-turn dirt races on the card had been run more than six hours earlier under very different track conditions. Which means the earlier dirt races cannot safely be used as a comparison. As with any such procedure, speed figures get ever more questionable the smaller the sample you draw from is (a fact that sometimes renders BSF's from racedays with sudden changes in weather essentially meaningless).

The only other race to compare the Derby to was the 13th, a 7f allowance for 3yo fillies won wire-to-wire by the favorite, who ran the whole race on what seemed to be a highly favorable rail. Results behind her didn’t match well with previous forms. Previous numbers are even less helpful for the Derby itself, as freaky trips, surprise performances and added distance necessarily result in a contradictory outcome.

The assessor, and I don’t know who it was in this case, had to completely turn the process on its head. Judging from only two races (both of them 3yo races with somewhat odd results) he can’t have done anything more than an educated guess on how fast the top finishers may have run, then deduct from there. Mine That Bird’s 105 could be correct, it could just as well be off by 5 points in either direction. Under such circumstances, a speed figure is a guess, not a handicapping tool. This isn't news, but it’s nonetheless an important fact that many racing fans too often forget about.

UPDATE: Steve Crist has written a piece on his DRF blog in which he provides a brief explanation of the methodology used to come up with the 105. It's definitely worth reading, but I don't think it devalues my arguments.


  1. Wrong. I was expecting a 108 Beyer for this race because of the GI status, the earnings requirement, the time 2:02 on a muddy track and the 6 length win. Beyers are an excellent handicapping tool so long as you do not become a slave to them. The 105 Beyer was reasonable and expected. A Beyer may not be a precision tool, but handicapping is part art and part science anyway. The Beyers are very useful, that is why people use them. Proof enough.

  2. It wasn't my intention to argue that BSF's are a bad handicapping tool (I use them as a major factor of my handicapping routine myself). I also made clear that I don't think the number is completely wrong. What I did argue is that it's not possible to give a reliable Beyer figure for a race where you have so few givens, such a small sample and so many asterisks. Just like you can't have a reliable Beyer for the last race on a card if 25 minutes before post time the weather changed from summer heat to rainstorm. Even the maintenance crew isn't able to precisely assess the extent of change in conditions.

    For what it's worth, some of my best handicapping decisions have been based on discounting Beyers that have come under such circumstances.

    That you shouldn't become a slave to the Beyers was exactly my point here.