On the Evolution of the Called Strike Zone in Major League Baseball from 2008-2023

Music City Center 

The accuracy and consistency with which home plate umpires call pitches can play a significant role in the outcomes of Major League Baseball (MLB) games. Here, we investigate trends in called pitch accuracy and within-game consistency for all regular season MLB games spanning 2008-2023, and using neural networks followed by the fitting of extended superelliptical models, we map the locations of these pitches to quantify how well the geometry of the called strike zone aligns with that of the rule-book strike zone in each season. Our results show that there was steady improvement in both accuracy and within-game consistency of the called strike zone, and that by 2023 its geometry aligned with that of the rule-book strike zone in every respect except its size, which was about 10% too large. The impact of these findings on the forthcoming implementation of a robo-ump challenge system in MLB is discussed.

sports statistics

misclassification rate

robo-umps

morphometrics 

Section on Statistics in Sports