Does VAR reduce referee bias? Causal evidence from global professional football leagues

The presence of home advantage and referee bias in professional football has been widely documented. This study empirically examines the impact of Video Assistant Referee (VAR) technology on mitigating referee bias toward the home team by using a large-scale dataset spanning 41 football leagues across 26 countries from 2013 to 2024. Using a staggered difference-in-differences model and the synthetic control method, we provide causal evidence on how VAR influences home advantage measured by goals, red cards, and penalties. Our findings indicate that VAR adoption significantly reduces home advantage by increasing the average number of goals scored by away teams, rather than decreasing home team goals. Furthermore, an increase in direct red cards was observed, with a greater effect on home teams than away teams. However, there was no significant difference in the number of penalty kicks before and after the introduction of VAR. Additional analyses reveal that VAR implementation significantly increases the probability of away wins, reinforcing the main findings. These results demonstrate the role of technological innovation in enhancing fairness in professional football. By employing robust econometric techniques and a comprehensive dataset, this study contributes to the ongoing discourse on sports technology and referee decision-making, offering insights into the long-term effects of VAR implementation on competitive balance.