This study estimates the effect of manager challenge in Major League Baseball to test whether momentum exists in sports. Despite much research over the last 30 years, the existence of momentum in sports remains controversial. Productivity of teams, measured by the number of runs in the inning, is analyzed by using 1,193 replay reviews during 2015-2019 regular season American League home games. Using a difference-in-differences methodology, this study fails to find statistically significant causal effect of winning a manager challenge on the team’s productivity on subsequent innings. However, there could still be a shorter- or longer-term momentum as this study analyzes the existence of a medium-term momentum that lasts for subsequent two innings. The finding could be generalized to other zero-sum settings where agents have option to challenge.




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