60-Second Tech

Umpires Show Bias for Stars and Strikes

Baseball's expanded review system excludes ball and strike calls, which a study finds to be biased in favor of star players, especially late in games. Larry Greenemeier reports


Now research reveals that even top-notch umps are subject to decision-making bias, often in a game’s most important moments. That’s according to a study to appear in an upcoming issue of the journal Management Science. [Jerry W. Kim and Brayden G. King, Seeing Stars: Matthew Effects and Status Bias in Major League Baseball Umpiring]
A team of Northwestern and Columbia university researchers analyzed more than 700,000 pitches thrown during the 2008 and 2009 seasons. They found that umpires called about 14 percent of nonswinging pitches wrong. And umps were least accurate when the game was on the line in the ninth inning and when calling a strike would end an at-bat. They also tended to favor All-Star pitchers, especially those with a reputation for good control.
Of course, there’s no way to know how challenging a handful of the hundreds of pitches thrown in any given game would affect the outcome. And you might create a different umpire bias—against managers who demand too many replays.

—Larry Greenemeier

[The above text is a transcript of this podcast.]

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