On a potential mercy rule for Major League Baseball

Abstract

Major League Baseball (MLB) games are getting lengthier, having gone up from an average of 2.5 hours in the 1970s to over three hours since 2012. Meanwhile, the average attendance in an MLB game has recently decreased from around 30,800 in 2012 to less than 28,300 in 2019. In this report, we consider a solution to shorten games and increase their entertainment value through implementing a mercy rule, also called a run rule, in which a game may end early in the case of a blowout. We analyze data from 24,296 MLB regular season games between 2010 and 2019 to identify potential mercy rules for which early termination is unlikely to affect the final result. We find that calling a game after the seventh inning if a team is up by seven or more runs will not change the outcome of a game 99.9% of the time, and this rule may impact about 10% of all games each season. In addition, this mercy rule will decrease the game time by an average of about 40 minutes. We then discuss the practical implementation of this rule.