Hurdle Models and Age Effects in the Major League Baseball Draft

Major League Baseball franchises expend an abundance of resources on scouting in preparation for the June Amateur Draft. In addition to the classic “tools†assessed, another factor considered is age: Younger players may get selected over older players of equal ability because of anticipated development. Additionally, Little League rules in effect until 2006 operated on an August 1–July 31 year meaning that, in their youth, players born on August 1 were the eldest in their cohort. We define a relative age to be how old a player was (in days) when the youngest player in their cohort was born. For example, a player born on July 31 would have a relative age of 1 day, whereas a player born on August 1 would have a relative age of 365 days. We examine the performance of high school (HS) players selected in the June Draft from 1987 to 2011. We find that more relatively old players are selected in the Draft. Conversely, both age and relative age have a significant negative relationship with the odds of reaching the major leagues. Given that a draftee reaches the majors, however, there is no difference based on age or relative age, as measured by games played, wins above replacement, and on-base plus slugging percentage. Had the draft market operated efficiently, neither relative age nor age on draft day would have captured additional variation in performance after controlling for draft position and other factors. We conclude that teams have undervalued both young and relatively young HS players.