It was the truism of the 1980s. “Since 1929, every Derby winner’s Dosage Index has been 4.00 or below.” Dosage Index numbers, a quantitative representation of pedigree qualities, were printed regularly in the Daily Racing Form. Journalists made casual mention to a horse’s Dosage Index when making assessments. Throughout the 1980s devotees cashed in by using the mystical numbers to improve their handicapping, often in conjunction with the “dual qualifier” system.   The index seemed destined to become an integral part of the handicapping quotient – particularly the Kentucky Derby.   Then came the 1990s.

In 1991, the winning horse, Strike It Gold, went into the Kentucky Derby as a horse with a Dosage Index (9.0) too high for consideration. However, based on the formula for assessing pedigree, Strike it Gold’s win elevated the status of his sire and, as a result, increased Strike It Gold’s Dosage index to a respectable 2.6. Perhaps because of the shift, and because this was the first contradiction to the theory, faith in the Dosage Index persisted; the theory remained intact. Then it happened again. In 1998 Real Quiet, with a Dosage Index of 5.29 (suggesting a pedigree with the lowest stamina in the field) won the 124^th Derby.   Then it happened again the next year.   In 1999 Charismatic won the Kentucky Derby with an index number of 5.22. The once-solid truism of the 1980s was beginning its fall from grace.

In 2005, when Giacomo -- with an Index number above 4.0 -- won, it was no longer news. By 2000, journalist Bill Finley declared, “Ding, dong, the dosage is dead” of the once-revered index. Others labeled it a “Fraud” and “bogus”. 

Last week, in Handicappers Reflect on the Kentucky Derby and Look Towards the Preakness Stakes, after the longshot win by Mine That Bird, we asked handicappers for their comments. Michael A. Gooley of Trackpro.com observed that Mine That Bird had the highest Dosage Index, followed by Musket Man and Pioneerof the Nile.   According to Gooley’s, horses at both ends of the Dosage Index spectrum deserve consideration. For many, this idea represents a rather unconventional approach. Haven’t Dosage Index adherents always advocated for disregarding horses with high numbers? Indeed, when staff from Case the Race contacted Steven Roman, author of Dosage: Pedigree and Performance and one of the original proponents of the Dosage Index, we could not confirm that the author intended for the index to be applied in this way.   Instead, Roman referred us to the following links:

The Trend of Derby DI Inflation Continues
Does Pedigree Matter in the Kentucky Derby...Again?
Racing Type vs Breeding Type in Contemporary Sires

When we followed up again with Gooley, he observed. “Winners of the Kentucky Derby have won at both ends of the Dosage Index and I think the tool does an excellent job of identifying the contenders in the Derby.  Below are the winners of the Kentucky Derby for this decade provided by BloodHorse.com and as you can see the Dosage Index is a powerful tool to use when handicapping the Kentucky Derby:  BIG BROWN and FUNNYCIDE won with a low Dosage Index that favored distance and stamina pedigrees,  but MINE THAT BIRD and GIACOMO won with speed pedigree as indicated by their high Dosage Index.  It also appears that the average Dosage Index is trending higher with recent winners.  Five of the winners listed below had a Dosage Index over 3.00. One possible way this knowledge can be applied to future Derby’s could be to narrow the large field in the Derby down to say six horses by taking the three horses with the highest dosage which worked splendidly this year, and then take the three horses with the lowest dosage index and apply fundamental handicapping factors from this group of six to hopefully identify the winner. This is just one way the dosage index can be used in my opinion but I do like the tool in general for handicapping the Kentucky Derby and I think it is very effective for this particular race.  No tool is perfect as we all know.”

Following are the Dosage Indexes for all the Derby winners this decade:

MINE THAT BIRD (2009) 5.40
Big Brown  (2008) 1.67
Street Sense  (2007) 2.14
Barbaro (2006) 2.41 
Giacomo (2005) 4.33
Smarty Jones  (2004) 3.40
Funny Cide (2003) 1.53
War Emblem(2002) 3.40
Monarchos   (2001) 1.40
Fusaichi Pegasus (2000) 3.67

From the site associated with Steven Roman, chef-de-race.com, we used the Triple Crown Table to determine some baseline numbers. Out of the 91 horses listed, the average Dosage Index is 2.963 and the median is 3.0. Horses with a Dosage Index greater than 4.0 comprise 7.7% of the pool. 

Based on the information available, it does appear that there is a trend toward higher Dosage Index numbers in the Kentucky. It could be that the cutoff number is rising. It could also be true that Gooley is right to bring attention to horses at either end of the spectrum.

As to the question of how to apply this information to handicapping … we’ll leave it up to you to decide.