Baseball umpires, 1915.

Umpiring baseball apparently comes with a degree of ethnic bias, as millions of pitch calls were analyzed and umpires displayed a persistent tendency to call pitches more favorably for members of their own ethnic group. Considering how few African-American baseball players there currently are and the lack of Latin American umpires, I wonder if that sample size had an effect on the study. An excerpt from an article on Ars Technica by John Timmer:

“Several studies have shown that sporting officials have a tendency to exhibit subtle biases in favor of members of their own ethnic group, So, an umpire that’s white might be expected to favor a white pitcher, giving him more favorable calls when pitches are at the edge of the strike zone. This sort of bias might be expected to be subtle, but the research has the sort of statistical power that comes from large numbers: a record of over 3.5 million pitches, and what their outcomes were. (Here, the authors turned to ESPN.com for a pitch-by-pitch record of the game to match up with their computer data.)

After eliminating things like foul balls, swinging strikes, and intentional balls, the authors still had a very impressive collection of data to work with: 1.9 million pitches in which the umpires made a decision. Then came the real drudge work. Using sources such as About.com and web searches, the authors pieced together the ethnic origins of all the major league players and umpires involved. And then they started crunching numbers. And what they found was a subtle bias that went away when the umpires thought someone was watching them.”

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Earl Weaver goes apeshit: