The Relative Age Effect in Top100 Female Tennis Players (2014–2018)

The theory of Relative Age Effect (RAE) works on the assumption that athletes born at the beginning of a calendar year are more successful than athletes born in the end of the year. The athletes born early have a significant probability of a higher level of physiological, mor-phological and psychological abilities than later born athletes. Several studies show that the RAE was not found in females or it was significantly lower than in males. The research objective was to find out the influence of RAE in WTA Tour TOP100 female professional tennis players (n=500) in 2014–2018. Cohen’s effect size (ES) w was calculated to assess the level of the influence of RAE. To assess the differences between the observed and the expected relative age quarter distribution, Chi-Square test (ꭕ2) was used. In terms of effect size (ES), a medium influence of RAE has been proven in 2016 and 2017 (w = 0.33, resp. w = 0.30); a small influence has been proven in years 2014, 2015, 2018 and in the whole observed period 2014–2018. Based on statistical analysis, the influence of RAE cannot be rejected in years 2016 (p 0.05). The next step was to assess the influence of RAE on the final WTA ranking in 2014–2018. Players have been divided into four intervals: 1–25, 26–50, 51–75 and 76–100 positions. ES has showed the medium influence of RAE in 76–100 positions (w = 0.34); only small influence of RAE was found in other positions. Statistical analysis showed that the influence of RAE cannot be rejected in 1–25, 26–50 and 76–100 positions (p < 0.05): it can be rejected in 54–75 positions. The results of the research have shown the medium influence of RAE in 2016 and 2017: in the recent years (and in the whole observed period of 2014–2018), the influence of RAE was small. The influence of RAE on the final WTA ranking is also small, except the 76–100 positions.