Do Referees Favor Home Teams in Football?
We analyzed referee bias towards home teams using extensive match data from European leagues.
1Data-Driven Approach to Football Debates
Football fans often show bias when judging referee decisions. Supporters of different teams can interpret the same foul completely differently. This study analyzed over 100,000 matches across 14 European leagues from 2017-2023 seasons. Data was sourced from football-data.co.uk, focusing on matches with consistent foul/yellow card recording.
2Methodology
The study used 'cards per foul' ratio rather than just yellow card counts, providing clearer insight into referee behavior. Additional factors like match predictions from betting odds, possession percentages, and halftime scores were controlled. COVID-era matches played without spectators were analyzed separately.
3Foul Distribution Across Leagues
Portugal's Primeira Liga leads with 29.4 fouls per match, followed by Italy's Serie B and Spain's La Liga. Northern European leagues (Premier League, Eredivisie) show fewer interruptions (21-22 fouls/match). Interestingly, home teams commit more fouls in Spain, Portugal and Turkey.
4Home Advantage in Yellow Cards
Consistently across all leagues, away teams receive 0.15-0.34 more yellow cards per match. This difference was highest in English Championship (0.34) and lowest in Serie A (0.15). When examining cards per foul ratio, home teams received 7.4% fewer punishments.
5Impact of Empty Stadiums
Matches played without spectators during COVID-19 provided crucial data on fan influence. Home advantage decreased significantly in empty stadiums, with the cards per foul difference dropping to 4.8%. This supports the theory of referee susceptibility to crowd pressure.
6Effect of Team Reputation
The analysis didn't confirm claims that 'big clubs get favorable treatment'. In Premier League, teams like Manchester City and Liverpool showed average cards per foul ratios. Barcelona received 6.2% fewer cards in Spain, but this wasn't statistically significant.
7Playing Style Factor
Teams with more possession naturally commit fewer fouls. However, data shows home teams receive fewer cards even with low possession. In Serie A, home teams with just 40% possession still received 5.8% fewer cards than away teams.
8Match Situation Influence
Halftime score significantly affects referee decisions. Teams trailing tend to play more aggressively. Yet home teams received fewer cards even when behind, with the difference increasing in second halves.
9Cultural Differences
Southern European leagues (Italy, Spain, Portugal) show higher foul counts but lower card tendencies. Northern leagues have fewer fouls but higher cards per foul ratios, possibly reflecting different football cultures.
10Referee Experience Matters
Comparing referees with over 300 matches to newcomers, experienced officials showed less home-away bias. UEFA's elite referees maintained just 2.1% home advantage in cards per foul ratio.
11VAR Impact
Matches using Video Assistant Referee technology showed reduced home advantage. Particularly in penalty decisions, home team penalty awards dropped from 14.3% to 9.7% with VAR intervention, demonstrating technology's role in reducing human bias.
12Conclusion and Football's Future
Data confirms referees show slight subconscious bias toward home teams (7.4% card advantage), though less than expected. Technological advancements (VAR, AI analysis) may further reduce this bias. Football authorities should incorporate these findings into referee training programs.
Original article: Towards Data Science — Hakemler Ev Sahibi Takımları Kayırıyor mu?