A Whole New Ballgame: Evaluating the Effects of Major League Baseball’s 2023 New Rules Using Statistical Modeling

Abstract

In 2023, three new rules were introduced to the game of professional baseball at the Major League level. The pitch timer, defensive shift limits, and increase in base size were years in the making, all having been individually tested in the Minor Leagues prior to their call up to “The Show”. While many different aspects of the game of baseball have seemingly been affected by said new rules, I investigate their affects on plate appearance outcomes and stolen base attempts by creating models of both situations on a by-pitch basis. I am able to use indicators to distinguish the impact of the different rules by utilizing a control year, 2023, and their respective testing seasons from Double-A and Triple-A in addition to MLB data.