Dosage and Two-Year-Olds

A fascinating and illustrative use of Dosage as a tool for understanding aptitudinal trends is revealed in its application to the analysis of two-year-old racing.  Specifically, we can monitor the moving average of the DI and the winning distance for winners of juvenile stakes throughout the year.  A moving average is simply a shifting average over a series of successive events.  The moving average changes with each additional data point.  In our example, we arranged the two-year-old stakes winners in chronological order for each of the years 1983 through 2007.  We then determined the average DI and the average distance for each of the races in sequence through the year.  In other words, we calculated the average DI and average distance for all of the first juvenile stakes from 1983 through 2007 then did the same for the second, the third and so on.  Finally, we plotted the changes in the average DI and average distance from race 1 through race 110, encompassing over 2800 races in all.  The result of the plot is displayed in the following chart.

Dosage Applied to Two-Year-Old Racing

Although there is considerable but not unexpected scatter within the data, the computer-generated trend lines are unequivocal and exactly as one would expect.  The average DI drops continuously throughout the year as the average distance of the races increases.  In fact, the two computer-generated curves are virtually mirror images of each other.  The analysis graphically captures the progression from the 4½-furlong "baby" races at Keeneland in April through the 8½ to 9 furlong races leading up to and beyond the Breeders' Cup, with speed-bred high DI horses dominating the early season races and more stamina-bred lower DI horses taking over in the fall.  Occasionally an April Keeneland juvenile such as Summer Squall will win a classic race, and another, such as Horse of the Year Favorite Trick, may go on to great things.  More often than not, however, the fall two-year-old races and the following year's three-year-old route races tend to be dominated by colts and fillies that come out in late spring and into the fall.