Propensity Score Matching (PSM) has become a popular approach to estimate causal treatment effects. It is widely applied when evaluating labour market policies, but empirical examples can be found in very diverse fields of study. Once the researcher has decided to use PSM, he is confronted with...

In this paper we investigate how the expulsion of a player influences the out-come of a football match. Common sense implies a negative impact for the affected team. However, an old football myth suggests that such an expulsion might also be beneficial since it increases the team spirit as well...