Football (soccer) enthusiasts suspected it, but now statistics is confirming it. After analysing all the matches of the Spanish league "La Liga" from the 2014-2015 season, two experts in sports science have found that the greater the difference on the scoreboard, the less stoppage time is added to the end of the game. When the score is tighter, however, referees tend to add more stoppage time when the team in the higher division is losing.
The stoppage time added by the referee following the obligatory 90 minutes of a football match is used to compensate for time lost due to substitutions, injuries, expulsions and other incidents that arise during the game, but it seems as though other factors also play a role according to a new study.
Researchers Carlos Lago, from the University of Vigo (Spain), and Maite Gómez, from the European University of Madrid, have confirmed that referees favour the big teams by reducing the extra time when these teams are ahead on the scoreboard. In contrast, and according to an article published in the journal 'Perceptual and motor skills', referees slightly draw out the match when the big teams are losing.
To carry out the study the authors relied on data from the 380 matches played in the Spanish league during the 2014-2015 season. They then took several variables into account -such as the difference in goals on the scoreboard, the playing level of each team, the number of red and yellow cards, player substitutions, the average number of assists and fouls committed- to see if any of them had an influence on the amount of stoppage time.
After applying a statistical method (called linear regression and widely used to identify relationships between variables), it was observed that the greater the difference on the scoreboard, the less stoppage time was given by the referee. In very tight matches, nevertheless, refs tend to add more seconds when the team in the higher division is losing, and fewer seconds when they are winning. The number of red cards and fouls also cause an increase in extra time.
"The typical complaint from less powerful teams regarding how referees treat big teams better might make sense," explains Carlos Lago, "as their decisions tend to benefit the higher‑ranked teams when the scoreboard is against them. Furthermore, the more important the difference between the clubs, the greater the advantage." As the inequality between the teams decreases, because either two big teams or two small teams are playing against each other, this statistical trend disappears.
A bias that also favours local teams
Previous studies had already demonstrated that pressure from local fans also has an influence on referees when it comes to adding on more or less time. In the Spanish league, specifically, referees add 112 more seconds when the home team is losing by one goal or winning with a minimal difference.
This bias in favour of local teams was also found at football matches of the Bundesliga (Germany), Serie A (Italy), Premier League (United Kingdom), Major League Soccer (USA and Canada) and of the Campeonato Brasileiro (Brazil) leagues.
According to Lago, "what is most troubling is that the partiality of some referees for local teams and big clubs seems to have a name and surname, meaning that refs with less experience are more affected by the noise around them; there are also referees who are more or less home-biased and show a greater or lesser tendency to benefit the big teams in specific situations."
The expert in sports science concludes with some recommendations: "improve referee training and prevent subjectivity in their decisions to the extent possible, which at present have not proven to be malicious, but simply human. Additionally, technology could also help, although referee bias can decrease if they are simply aware of the role they play in the outcome of the matches."
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