Dear Baseball, we empathize:
Calling balls and strikes would seem to be one of the last bastions of the low-tech world; it’s all up to the judgement of the lone umpire behind home plate, and there’s no instant replay. But that impression would be badly wrong. In recent years, every stadium in the major leagues has been equipped with a QuesTec system that compares umpires’ ball and strike calls to an objective, computer-validated standard. Deviate too far from what the system says you should be calling, and you’ll automatically have your performance reviewed. This provides the ultimate “someone is watching you” experience for the umpire.
In its simplest form, when an umpire was from the same ethnic group as the pitcher, they were more likely to call a pitch a strike, at least at a ball park that was not equipped with a QuesTec monitor. When the same analysis was performed at a QuesTec game, the probability that a pitch would be called a strike when there was matching pitcher/ump ethnicity dropped by a full percent—”more than offsetting the favoritism shown by umpires when QuesTec does not monitor them.”