Abstract
This study is the first to investigate whether the introduction of additional assistant referees in the UEFA Europa League (2009–2010 season) and the UEFA Champions League (2010–2011 season) was associated with lower referee bias in terms of home and “big” team favouritism. To this end, we analyse a unique database with pre- and within-game characteristics of all games in seven recent seasons in these leagues by means of bivariate probit regression models. We find evidence for substantial referee bias before the introduction of additional referees, while no such evidence is found after the introduction. Furthermore, additional assistants go hand in hand with more yellow cards for both home and away teams. We show that these findings are robust to multiple operationalisations of referee bias and that they are not just picking up a general time evolution towards less referee bias or the effect of parallel reforms.
Highlights
Soccer referees are often accused of partial decision-making
We investigated whether this home advantage in receiving yellow cards is related to referee bias
We investigated the presence of referee bias in the 2007–2014 Union of European Football Association (UEFA) Europa and Champions Leagues
Summary
Soccer referees are often accused of partial decision-making. For example, after the 2016–2017 season quarter-final return of the Union of European Football Association (UEFA) Champions League between Real Madrid and Bayern Munich, the referee was criticised for giving an unjustified second yellow card to Bayern Munich player Vidal and not giving a second yellow card to Real Madrid player Casemiro [1]. Other famous controversial cases are the 2016–2017 season quarter-final return of the UEFA Champions League between FC Barcelona and Paris Saint-Germain [2] and the 2012–2013 season quarter-final return of the UEFA Champions League between Dortmund and Malaga [3]. These criticisms suggest that the referee’s decisions were biased. Referee bias may be defined as systematic decisions in favour of certain teams such as home or “big” teams, which are considered to be unfair Such a preferential treatment, which can result from conscious bias as well as from human error or incompetence, may have
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