The effect of reducing the number of matches in round-robin tournaments with four teams: evidence from beach volleyball
利用2017年职业沙滩排球赛制改革（循环赛阶段每队比赛从3场减至2场），基于6976场比赛数据，发现减少比赛场次不影响强队获胜概率和赛事有效性。
Abstract In recent years, many sports tournaments have increased the number of participating teams, which resulted in larger number of matches. These expansions have raised many calls to reduce the number of matches because of significant logistical and physiological concerns. This paper examines the effects of reducing the number of matches in a widely used round-robin tournament format featuring four teams. We leverage a 2017 structural change in professional beach volleyball, where the number of matches per team in the round-robin (pool) stage was reduced from three to two. Utilising data from 6976 matches, our multivariate regression analyses reveal that this reduction does not impact the probability of a favourite team winning a single match nor the overall tournament's efficacy, measured by the final standings' alignment with teams' initial strengths. These findings hold across different strength definitions and genders. Our study offers insights for sports seeking to expand the number of teams while preserving a four-team round-robin structure.