Tennis Serve Clock Started Ticking and Betting Market Inefficiencies Followed

Abstract

In 2020, men’s professional tennis adopted the so-called “serve clock,” which limited players to taking 25 seconds between points. Prior to the rule change, players could take unlimited time between points, so the serve clock forced many players to play more quickly than they would prefer, a change that, at the time, was thought to give players who possessed an abundance of certain physical characteristics or tennis-specific skills a better chance to withstand the increased physical rigors that the updated game placed on players. We set out to accomplish two tasks in analyzing how professional tennis changed with the implementation of the serve clock. First, we want to update for the serve clock era findings from previous studies that found tennis players who could save or convert break points and win first serve points were relatively better than their competition were more likely to win matches. Second, we want to determine how efficiently betting markets reacted to the implementation of the serve clock.
With data from results and odds of 11000 matches from five seasons of professional tennis, we use logit modeling of match results to determine that there was no increase in the rate of return to tennis-specific skills in the serve clock era, that relatively younger and taller players have gained advantages since the rule change occurred, and that betting markets were slow to detect information that allowed for more accurate predictions of matches, leading to a window of time in which larger than normal returns to bettors were available. We believe our findings warrant further investigation of the efficiency of betting markets, especially in periods in which structural changes add to the uncertainty of predicting results.