Positional relative age effect in europe's top ten football leagues.

Background: A previous study confirmed the existence of the relative age effect (RAE) in the top ten leagues of the Union of European Football Associations (UEFA) during the 2016-2017 season, reporting that the effect was particularly pronounced among defenders and midfielders. The present study investigates whether this effect persists. Specifically, it aims to examine the RAE among professional male footballers in UEFA's top ten leagues during the 2023-2024 season, and to explore how the effect varies by playing position and league.

Methods: The study analysed the birthdates and playing positions of 5,238 professional footballers. Birthdates were categorised into four quartiles: Q1 (January 1 to March 31), Q2 (April 1 to June 30), Q3 (July 1 to September 30), and Q4 (October 1 to December 31), and were examined in detail by league and position.

Results: Players born in Q1 (30.3%) were overrepresented compared to those born in Q4 (20.5%) (χ² = 132.470, p < .05). This difference was statistically significant in most leagues, particularly in Serie A (χ² = 33.535, V = 0.14), Ligue 1 (χ² = 23.741, V = 0.11), LaLiga (χ² = 22.491, V = 0.12), and Bundesliga (χ² = 21.681, V = 0.12), but not in Premier League (χ² = 1.665, p = .645). In terms of playing position, the RAE was present across all groups (p < .05), with the most pronounced effect observed among goalkeepers (χ² = 40.006, V = 0.15). Positional RAE patterns varied across leagues: significant differences were found for goalkeepers in Serie A, Süper Lig, and LaLiga; for defenders in LaLiga and Jupiler Pro League; for midfielders in Serie A, Ligue 1, Süper Lig, and Eredivisie; and for forwards in Ligue 1, Bundesliga, and Scottish Premiership (p < .05).

Conclusion: The findings indicate that the RAE persists in professional football within UEFA's top leagues. The effect is evident across all playing positions and varies by league context.