The relative age and birth order effect in Japanese professional football

Abstract

This study examines how the probability of becoming a professional football player depends on the birth month (relative age effect) and birth order. These two factors are random and cannot be controlled by the athlete. If these factors influence the probability of the occurrence of top athletes, they not only create inequality but also close the disciplines to potentially talented athletes, lowering the level of competition. Therefore, in this study, we statistically clarified the presence or absence of “giftedness of life” by focusing on the birth month and birth order of professional football league players in the Japan Professional Football League (J-League). Our results indicate that the probability of the occurrence of J-League players decreases significantly with increasing birth order and birth month (180 days, from April onward). Moreover, we found that second-born players with an older brother had higher estimated salaries than players without siblings. These results reveal the characteristics of excellent football players and suggest the importance and direction of improvement in talent discovery and development in sports. Based on our results, we recommend improvements in the player training system to buffer the effects of relative age effect and birth order.

A game for the ages: Understanding and overcoming the relative age effect in Australian football

“…Studies have confirmed this effect across a variety of sports globally, including American football, 2 athletics, 3 basketball, 4 baseball, 5 rugby, 6 football/soccer, 7,8 and ice hockey again. 9 There has also been a number of extensive literature reviews written.…”

The Relative-Age Effect in Male Japanese Football: A CrossSectional Analysis from Youth to Senior Competitive Level

“…Kawai, et al [17] also investigated U7-U12 grassroots football and found RAE in U9 and U12 categories. Yamamoto, et al [18] explored the probability of becoming a professional player based on birth month and birth order in the J.LEAGUE and found a significant RAE. Further research within elite youth football by Hirose and Hirano [19] examined the relationship between birth month distribution and biological maturation in U9 -U16 players in a J.LEAGUE academy, which explored significant RAE in all age groups, but without evidence of statistically significant differences between biological maturation and birth months.…”