No relevant spectator impact on home advantage in male and female professional volleyball - A longitudinal multilevel logistic model analysis over 25 years.

Home advantage (HA) regularly occurs in volleyball (Pollard et al., 2017: men: 56.62%, women: 55.26%). Research to date has investigated primarily small samples of mostly female matches and not looked into the potential impact of spectators on HA. This archival analysis uses multilevel modelling to examine HA in professional German volleyball (men & women) over 25 seasons in all regular and play-off matches (N = 6,833). We analyze how spectators drive HA and whether this projects to the COVID-19 season 2020/21. When intercepts varied between teams (2-level model, ICC = 27%), the winning probability increased when playing at home (men: 57.01%, ORmen = 2.39, d = 0.48; women: 55.39%, ORwomen = 2.19, d = 0.43), while controlling for team strength, interaction with gender, and travelling distance. More spectators had a negligible effect on the men's and women's chances (|d| < 0.07). Similar trends were observed for the probability of winning sets. Contrary to other team sports (e.g., soccer), there is no HA-development over the last decades.