Calling Balls and Strikes: Estimating the Effects of Extreme Temperatures on Labour Productivity.

Abstract

This paper seeks to explore the relationship between temperatures and labour productivity, in the realm of Major League Baseball (MLB). MLB umpires exposed to outdoor temperatures have to rely on mental concentration to judge positions of balls at the home plate, and are subject to inaccurate judgments at times. Using advanced technology at baseball ballparks, I establish a measure of umpire accuracy, as a measure of labour productivity, for 7140 baseball games from 2014 to 2016. The relationship of interest is estimated by a fixed effects model with relevant weather and other controls, finding a 0.62 percentage points decrease in umpire accuracy in games held above 33.9°C, relative to games held between temperatures of 8.3°C and 33.9°C. This sign and magnitude remain stable to alternative weather data controls and robustness checks. No statistically significant relationship was found for low-end temperatures below 8.3°C and umpire accuracy.