The Swiss-system is an increasingly popular competition format as it provides a favourable trade-off between the number of matches and ranking accuracy. However, there is no empirical study on the potential unfairness of Swiss-system chess tournaments caused by the odd number of rounds played. To analyse this issue, our paper compares the number of points scored in the tournament between players who played one game more with the white pieces and players who played one game less with the white pieces. Using data from 28 highly prestigious competitions, we find that players with an extra white game score significantly more points. In particular, the advantage exceeds the value of a draw in the four Grand Swiss tournaments. A potential solution to this unfairness could be organising Swiss-system chess tournaments with an even number of rounds, and guaranteeing a balanced colour assignment for all players using a recently proposed pairing mechanism.

翻译：瑞士制因其在比赛场次与排名准确性之间提供了有利的权衡，正成为一种日益流行的竞赛形式。然而，目前尚无实证研究探讨因奇数轮次比赛而可能导致的瑞士制国际象棋锦标赛不公平问题。为分析此问题，本文比较了在锦标赛中多执白棋一局与少执白棋一局的选手所获得的积分差异。基于28项高规格赛事的数据分析，我们发现多执白棋一局的选手得分显著更高。特别是在四场大瑞士制锦标赛中，这一优势超过了和棋的价值。针对该公平性问题的潜在解决方案包括：采用偶数轮次组织瑞士制国际象棋锦标赛，并运用近期提出的配对机制确保所有选手获得平衡的执棋颜色分配。