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Abstract:
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Recent work has shown that relatively precise ball tracking technology used to monitor MLB umpires has resulted in considerable improvement in ball-strike call accuracy at the expense of total offense. Given that players tend to have heterogeneous skillsets, these changes may impact players differentially, potentially resulting in lower salaries for some. If so, union officials have good reason to demand a role in negotiations on enforcement of policy largely external to players themselves. This work therefore uses pitch-level data on umpire ball-strike calls, known as PITCHf/x, to estimate changes in batter productivity stemming from changes in the called strike zone. I begin by estimating pitch location-specific differences in run expectancies with the 2008 MLB season using a generalized additive model. Pitch-level error terms are then aggregated at the player level to identify deviation in performance from the league-level expectation across pitch locations. Finally, these aggregations are applied in the context of the changes in the strike zone and shifts in pitch location choices in subsequent seasons to arrive at expected performance and salary impacts for individual players.
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