This article addresses the issue of contestant heterogeneity (CH) in team efforts in National Basketball Association games for the three seasons from 2013/14 to 2015/16. The results show that two teams’ total efforts regarding rebounds and fouls increase as CH becomes smaller. The evidence thus indicates that the two teams play harder the smaller that CH is. In the analysis of the effects of heterogeneity on the favorite’s and the underdog’s efforts, the results show that each tries harder when CH is reduced and makes less effort as it becomes larger. These results support the contamination hypothesis. The checks for robustness in the panel regressions and results of Hack-a-Shaq strategy reinforce these conclusions. The evidence also shows that the appearance of the previous year’s champion in a game decreases the two teams’ total number of rebounds and fouls. Overwhelming CH makes both favorites and underdogs exert less effort.
JEL: D1, J44, L83