While CABI is best known for its involvement in agriculture and the environment, the CAB Abstracts database also covers a range of other subjects, including leisure, tourism and sport. As one of the editors covering this subject area, from time to time I come across papers on subjects close to my heart. Most recently, football, and the bias of referees.
It’s the firm belief of soccer fans that away teams never get decisions in their favour at certain big clubs. Supporters of less fashionable teams – such as myself – are also convinced that decisions rarely go their way when playing the Premiership giants. Two recent papers add support to the view that referees are biased in favour of the home team, and fans will also not be surprised to find that some referees are more prone to this behaviour than others.
A study by Dawson et al. (2007) published in the Journal of the Royal Statistical Society looked at yellow and red cards issued over a seven year period in the English Premier League. These were used to test a number of hypotheses relating to refereeing consistency and bias. Among the findings, the study reports that relative team strengths matter: underdogs tend to incur a higher rate of disciplinary sanction than favourites (no surprise to supporters of smaller clubs, who have long believed that they rarely get a favourable decision when playing against Manchester United or Liverpool). And it is found that a tendency for away teams to incur more disciplinary points than home teams cannot be attributed to the home advantage effect on match results, and appears to be due to a refereeing bias favouring the home team. This interpretation is consistent with evidence of home team bias in several other recent studies, which find that the home team is favoured in the calling of fouls, or in the addition of stoppage time at the end of matches. Finally, evidence is found of variation between referees in the degree of home team bias (fans call certain referees ‘homers’ for their propensity to favour the home side), and this variation contributes to the overall pattern of inconsistency in refereeing. The authors suggest that, although all referees should be counselled and encouraged to avoid (presumably unintentional) home team bias in their decision-making, the extent to which corrective action is required is also likely to vary between officials.
Boyko et al. (2007) also examined possible referee bias in the English Premiership, measuring variation in goal differential between the home and away teams in 5244 matches involving 50 referees. This study also found that home bias varied between referees, with the significance of the result depending on one (sadly unnamed, though I have my suspicions) referee with a particularly high home advantage. Referees were found to vary significantly in their yellow card and penalty differentials even excluding this individual referee. It is concluded that referees are responsible for some of the observed home advantage in the Premiership, and suggested that home advantage is dependent on the subjective decisions of referees that vary between individuals. The authors hypothesize that individual referees respond differently to factors such as crowd noise (a previous paper by Nevill et al., 2002, found an effect of crowd noise on decisions of referees viewing matches on videotape) and suggest further research looking at referees’ psychological and behavioural responses to biased crowds.
Downward and Jones (2007) looked at yellow cards issued in the English FA Cup in relation to crowd size. Overall, a significantly higher number of yellow cards were awarded against the away team, and the probability of a yellow card being awarded against the home team decreased as crowd size increased. One of the possible explanations is that referees may seek to appease the crowd and are more likely to do so as crowd size increases.
Knowing that their feelings of rough justice are backed up by statistical evidence will not be of much consolation to fans of teams that have seen a player harshly sent off against Manchester United at Old Trafford, or been denied a clear-cut penalty against Liverpool at Anfield. They can only hope that the results of these studies will be passed on to referees and the football authorities and contribute to better awareness and training for the men with the whistles. In the meantime, it gives those fans who feel that their teams are harshly done to by referees a bit more evidence when we bore anyone who will listen with the story of how the referee was against us.