Data Sheet 1_When technology meets judgment: outcome of football referees’ disciplinary decision-making after the implementation of VAR in the English Premier League.docx

IntroductionVideo Assistant Referee (VAR) is a decision-support system that helps referees make more accurate decisions and eliminate clear and obvious errors. However, the implementation of VAR in world football has been one of the most significant and controversial technological procedures used.
MethodsThis study examines how the introduction of VAR has affected refereeing decisions in the English Premier League (EPL) by examining the number of red cards and penalties per match. Yellow cards were also implemented in the analyses as a possible hypothesis-generating cause. Using match-level data from the 2018/19 season (without-VAR) and the 2023/24 season (with-VAR), and using the English Championship as a control group, we apply a difference-in-differences (DiD) analysis to estimate the contributive effect of VAR’s impact on three key outcomes: red cards, penalties and yellow cards awarded per match.
ResultsThe results suggest a statistically significant increase in all three outcomes in the Premier League following the introduction of VAR, compared to the Championship where VAR was not implemented. The increase in red cards and penalties, both explicitly governed by the VAR protocol, likely reflects improved identification of clear and obvious errors. The observed rise in yellow cards suggests that VAR may exert an indirect influence on referee’s behaviour, although this finding needs further investigation to be verified.
DiscussionNotably, the estimates found in current study reflect only differences between the Premier League and the Championship and no further definitive causal effects should be drawn. This study contributes to the ongoing debate about VAR’s role and potential impact on football referees’ disciplinary decision-making behaviour and provides a foundation for further empirical research on the broader implications of VAR in football.