A growing group of social scientists are researching peer learning, looking to answer the question “does an individual learn from their network?” In this post, I’ll present some evidence that MLB umpires “learn” from their peers in their assigned crews.

To quantify this, I calculate “call quality” for each umpire in each season from 2008 to 2019. Call quality is determined in a similar way to many umpire score card measures: I take PITCHf/x data for each game that a given umpire was assigned to home plate, subset to all called strikes and called balls, and overlay the true strike zone to calculate the proportion of correct calls.

I’m specifically interested in whether an umpire’s call quality is driven by the call quality of umpires they have been assigned to work with in the past. Read the rest of this entry »