nep-spo New Economics Papers
on Sports and Economics
Issue of 2022‒04‒11
two papers chosen by
Humberto Barreto
DePauw University

  1. Evaluating probabilistic forecasts of football matches: the case against the ranked probability score By Wheatcroft, Edward
  2. In-group Favoritism and Peer Effects in Wrongful Acquittals: NBA Referees as Judges By Naci H. Mocan; Eric Osborne-Christenson

  1. By: Wheatcroft, Edward
    Abstract: A scoring rule is a function of a probabilistic forecast and a corresponding outcome used to evaluate forecast performance. There is some debate as to which scoring rules are most appropriate for evaluating forecasts of sporting events. This paper focuses on forecasts of the outcomes of football matches. The ranked probability score (RPS) is often recommended since it is 'sensitive to distance', that is it takes into account the ordering in the outcomes (a home win is 'closer' to a draw than it is to an away win). In this paper, this reasoning is disputed on the basis that it adds nothing in terms of the usual aims of using scoring rules. A local scoring rule is one that only takes the probability placed on the outcome into consideration. Two simulation experiments are carried out to compare the performance of the RPS, which is non-local and sensitive to distance, the Brier score, which is non-local and insensitive to distance, and the Ignorance score, which is local and insensitive to distance. The Ignorance score outperforms both the RPS and the Brier score, casting doubt on the value of non-locality and sensitivity to distance as properties of scoring rules in this context.
    Keywords: football forecasting; forecast evaluation; ignorance score; ranked probability score; scoring rules
    JEL: C1
    Date: 2021–12–01
  2. By: Naci H. Mocan; Eric Osborne-Christenson
    Abstract: We provide the first analysis of racial in-group bias in Type-I and Type-II errors. Using player-referee matched data from NBA games we show that there is no overall racial bias or in-group bias in foul calls made by referees. Similarly, there is no racial bias or in-group bias in Type-I errors (incorrect foul calls). On the other hand, there is significant in-group favoritism in Type-II errors. These are wrongful acquittals where the referee did not blow the whistle although a foul was committed. We also analyze peer effects and find that black referees’ proclivity to make Type-II errors in favor of black players exists as long black referees have at least one black peer referee on the court, and that the bias disappears only if black referees have two white peers. In case of white referees, in-group favoritism in Type-II errors emerges if white referees have two black peers with them on the court. We provide evidence showing that the results are not attributable to skill differences between referees. We also show that a higher Type-I error rate during the season lowers referees’ probability to be selected to officiate a game in the playoffs, whereas variations in the rate of Type-II errors have no impact on the likelihood of a playoff assignment. These results indicate that in-group favoritism takes place in a domain which is not costly (making Type-II errors), and that bias is eliminated when it is costly to the decisionmaker.
    JEL: D03 D9 J70 K0
    Date: 2022–03

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