One of the main objectives of those involved in elite sports (parents, coaches, scientists, managers, etc.) is to understand what factors make success possible. The influence of a players’ birth month is an aspect that has attracted great interest, looking at how it impacts on the probability of having a successful sports career. In youth categories, players who were born between 1^st January and 31^st December of the same year are grouped in the same competition category. However, the personal development of children born in the first months of the year tends to be far ahead of those born in November or December. That maturation difference is known as the Relative Age Effect (RAE).^2,3,4 Having boys and girls with an advanced biological development compared to their opponents makes it easier to win matches and championships, although the one who loses might have more technical-tactical talent. This focus on winning at an early age can lead to the selection of the most biologically advanced children, despite their more limited talent. But how important is birth date in football player’s sports career?

A recent publication⁴ has analysed the birth dates and sports career success of 1071 football players belonging to the same elite club during the last 20 years. Players were grouped into 6 categories at the time they joined the club: U-12 (n=474), U-14 (n=167), U-16 (n=182), U-19 (n=121), in addition to the Filial team (n=192) and the First Team (n=35). The players’ birth date was divided into 4 categories: Group 1, those born in the first quarter of the year (between 1^st January and 31^st March); Group 2, in the second quarter (between 1^st April and 30^th June); Group 3, in the third quarter (between 1^st July and 31^st) September and finally, Group 4, in the fourth quarter (between 1^st October and 31^st December).

The results of the study suggest two very relevant conclusions: (i) Players born in the first quarter of the year are more likely to play in a professional club and reach the elite than those born in the last quarter, which confirms the detrimental effect of the RAE in young players. The number of players born in the first and second quarter of the year was significantly higher (p<0.01) than that of those born in the third and fourth quarter in U-12, U-14, U-16 and U-19, categories, and reserve team. In the First Team, no significant differences were observed, although a similar distribution was maintained. The percentage of players born in the first quarter in each of the categories was 45.4 (U-12), 46.5 (U-14), 50.9 (U-16), 44.5 (U 19), 39.8 (Filial) and 36.4 (First Team). As for the moment in which they joined the club, 45.1% of players were born in the first quarter and barely 10.1% in the fourth quarter. (ii) However, once a young player has passed the selection process and is signed by a club, the probabilities of then becoming a professional player are higher compared to  players born in the first quarter of the year. A player’s probability of reaching a professional level was 3 times higher in players born in the fourth quarter compared to those born in the first quarter. Of the 40 players (4.7% of the total) who reached that level, 18 were born in the first quarter and 9 in the fourth. It means that, while 11.1% of those born in the first quarter reached a professional level, only 4.5% of those born in the fourth quarter achieved it.

In conclusion, sports clubs should not be confused by success when working with  the younger players. We already know that supporting children with premature maturational development increases the probabilities of winning matches and  tournaments. Rather, it is about betting on talent, even if it comes from biologically less advanced players who cannot ensure short term success. Biological development is corrected and equalised; technical-tactical talent is not. The Relative Age Effect can lead us to potentially dismiss children who might actually be very able to reach the top level.

Carlos Lago Peñas

References:

¹ Brustio, P. R., Lupo, C., Ungureanu, A. N., Frati, R., Rainoldi, A., & Boccia, G. (2018). The relative age effect is larger in Italian soccer top-level youth categories and smaller in Serie PloS one, 13(4), e0196253.

² Cobley, S., McKenna, J., Baker, J., & Wattie, N. (2009). How pervasive are relative age effects in secondary school education? Journal of Educational Psychology, 101(2), 520.

³ Musch, J., & Grondin, S. (2001). Unequal competition as an impediment to personal development: A review of the relative age effect in sport. Developmental review, 21(2), 147-167.

⁴ Gil, S.M., Bidaurrazaga-Letona, I., Martin-Garetxana, I., Lekue, J.A., & Larruskain, J. (2019). Does birth date influence career attainment in professional soccer? Science and Medicine in Football, DOI: 10.1080/24733938.2019.1696471