Does birth date influence career attainment in professional soccer?

ABSTRACT Purpose: The aim of the study was to ascertain the influence of relative age on entry to a professional soccer club and on long-term career attainment. Methods: We analysed the birth dates (divided into four birth quarters, BQ) and the career attainment of 1071 soccer players who entered their club in the under 12 (U12), U14, U16, U19, Reserves and First Team groups. Results: There was an overrepresentation of players born in BQ1 in all groups except from the Reserves and First Team. Forty players (4.7%) became professional, 18 born in BQ1 and 9 in BQ4. More players born in BQ4 who had entered the club in the U12 and U14 groups became professional, compared to players born in the rest of the quarters. The odds for a player born in BQ4 to become professional were 3 times larger, 95% CI [1.38, 6.56] than players born in the rest of the BQs. Conclusions: The overrepresentation of relatively older players is evident among players that entered the club at younger ages. Although this overrepresentation declines with increasing age, it influences career attainment. Interestingly, once relatively young players are within the club, their chances to become professional are larger.