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This paper is concerned with the effect of nonmonetary incentives on behavior, in particular with the study of social pressure as a determinant of corruption. We offer empirical evidence that shows how professional soccer referees favor home teams in order to satisfy the crowds in the stadium. Referees have discretion over the addition of extra time at the end of a soccer game to compensate for lost time due to unusual stoppages. We find that referees systematically favor home teams by shortening close games where the home team is ahead, and lengthening close games where the home team is behind. They show no such bias for games that are not close. We further find that when the rewards for winning games increase, referees change their bias accordingly. Lastly, we identify that the mechanism through which bias operates is to satisfy the crowd, by documenting how the size and composition of the crowd affect referee favoritism. © 2005 President and Fellows of Harvard College and the Massachusetts Institute of Technology.