How the 12th Man Influences Football Matches: The Role of Fans and Referees in the Home Advantage Phenomenon

Does video assistant referee technology change the magnitude and direction of home advantages and referee bias? A proof-of-concept study

BACKGROUND

This study analyzed how Video Assistant Referee (VAR), introduced to improve the accuracy of referee decisions in football, changes the magnitude and direction of home advantage and referee bias in the Turkish Super League.

METHODS

We analyzed points, goals, yellow cards and red cards, fouls, penalties, and offside data from 1,838 matches played in the Turkish Super League with and without VAR. Two-sample t-tests and two one-sided tests analysis were applied to determine the differences between the home and away team data between the seasons played with and without VAR.

RESULTS

The findings revealed that the only variable that changed significantly after VAR was implemented was fouls, which decreased for both home (p <.001; d = 0.56, medium effect) and away teams (p <.001; d = 0.69, medium effect). The results also indicated that, with or without VAR, home teams had an advantage over away teams in points and goals, and away teams faced more referee bias regarding yellow cards and penalties (against).

CONCLUSIONS

Although this study shows that VAR does not significantly impact the HA and referee bias of football matches, nevertheless, teams should be more aware that bias is reduced when playing away. In addition, this study offers some practical applications that can help football players, coaches, and match officials better understand VAR technology's effects on HA and referee bias.

Home Advantage and Referee Bias: A Comparative Analysis of League Level Differences

Home advantage (HA) and referee bias are two important phenomena in football (soccer) and are frequently investigated by researchers. This study focused on analyzing HA and referee bias at different league levels. The study included 632 matches played in Turkey's top two leagues during the 2022-2023 season. Both leagues showed statistically significant game outcome differences between home and away teams regarding points, goals, shots, shots on target, passes, accurate passes, and ball possessions, indicating a HA. However, regarding referee bias, this study found that only Level 1 teams significantly differed in penalties and that this difference was not evident after analyzing for Bayes factors. Among Level 2 teams, as there was no statistical difference between home and away teams on any parameter indicating referee bias, and all Bayes factors indices were between 3.92-11.15, the null hypothesis was supported. Therefore, the results revealed a HA at both league levels, but a referee bias was not present in either league. This study emphasized that the HA phenomenon is clear and still evident in elite football and sub-elite leagues.