We show that professional soccer players exhibit reference-dependent behavior during matches. Controlling for the state of the match and for unobserved heterogeneity, we show on a minute-by-minute basis that a player breaches the rules of the game, measured by the referee's assignment of cards, with a significantly higher probability if his team is behind the expected match outcome, measured by pre-play betting odds of large professional bookmakers. We derive these results in two independent

more »

... a sets, one from ten seasons of the German Bundesliga, the other from eight seasons the English Premier League, each with more than half a million minutes of play. JEL classification: D03, D81, D84, L83