Relative age effect on national basketball teams around the world: Analysis by sex, age, location and world ranking

Abstract

Purpose: This study aimed to verify the presence of relative age effect (RAE) in a worldwide basketball sample, considering gender, age (youth and adult), FIBA World ranking position, and FIBA region. Methods: Date of birth data was extracted from the FIBA official open-access website and was grouped according to the month of birth and stratified into quarters such as January to March (Q1), April to June (Q2), July to September (Q3), and October to December (Q4). Chi-square tests were used to identify possible discrepancies in the frequency of births among trimesters, and the odds ratio was calculated between the number of birthdates in Q1 vs. Q4. Results: The sample consisted of 8664 athletes (3889 female and 4775 male), representing 140 countries, from U14 to adult categories. RAE was present in all analysis factors, except for Oceania players. The most prominent discrepancies were shown by male teams, U14 and U15 teams, FIBA world top-ranking teams, and FIBA Americas teams. In the adult category, although still present, RAE showed a trend to be reversed. Conclusions: There was an overrepresentation of early-born athletes, regardless of the factor of analysis, although the causes for RAE remain unclear.