Sentiment and bias in performance evaluation by impartial arbitrators

This study investigates whether relative performance evaluations of labor output are biased in the presence of sentiment, even when the (supposedly independent) evaluators are external. Data from a field-experiment setting—involving a pro-sport League's best-player award—allows for empirical testing of this proposition. After controlling for within-match performance, the results show that the match officials provide significantly better evaluations to players celebrating a ‘milestone’ game—an occasion on which sentimental favorites exist. However, this sentiment bias holds only in certain cases, and appears to have weakened in more recent years.