The Effect of Age on Thoroughbred Racing Performance

Using a dataset of 274 male Thoroughbred racehorses in the United States, we study theeffect of age on racing performance. Beyer speed figures, which are uniform measures ofracing performance across distance and racing surface, are utilized in this study. Asystem of equations is estimated to determine quadratic improvement and decline in racingperformance. We find that a typical horse’s peak racing age is 4.45 years. The rate ofimprovement from age 2 to 4 1/2 is greater than the rate of decline after age 4 1/2. Atypical horse will improve by 10 (horse) lengths in sprints (less than 1 mile) and 15lengths in routes (one mile or greater) from age 2 to 4 1/2. Over the next five years thetypical decline is 6 lengths for sprints and 9 1/2 lengths for routes.