The Relative Age Effect (RAE) in Japanese professional soccer players (J1 and J2) according to the selection process

Abstract

  The purpose of this study was to observe the RAE on soccer players of J1 and J2 according to the selection process.

  We analyzed 1,019 male J1 and J2 players born in 1980-2001. There were four groups based on the selection process: U18 / Pro, U18 / University / Pro, High School / Pro, and High School / University / Pro. Based on previous studies, the birth months of athletes were classified into Q1 (April-June), Q2 (July-September), Q3 (October-December), and Q4 (January-March). In order to examine the bias of the target group, the expected value of the target group was calculated based on the number of births of Japanese boys by month from 1980 to 2001, which is the same year as the target athlete, and the χ2 goodness-of-fit tests was performed to observe the RAE.

  An analysis of both the entire J-League and the four groups based on the selection process revealed RAE. There were significantly more athletes born early in the selection year than athletes born late in the year. In a group of high school / university / professional, Q1 was lower than the standard value appearance rate, showing a different tendency from other three groups.

  It is important to devise and implement a selection system that reduces the number of late-maturing athletes overlooked and dropped out during the selection process and allows athletes to have a chance of success regardless of RAE.