The Relative Age Effect among Elite American Youth Soccer Players
Glamser, Francis D., Vincent, John, Journal of Sport Behavior
Children are frequently grouped by age for school or sport activities in order to control for the effects of intellectual and physical development. However, even when groupings are limited to 1 -year categories, developmental differences can be great (DeMeis & Stearns, 1992). In such cases, some children will be almost a year older than other children. The outcome of this advantage has been termed the relative age effect (RAE) or the birth date effect.
Youth sport programs use cutoff dates to ensure that children will receive age appropriate instruction and to allow for fair competition. However, a large body of research has made it clear that the age differences within a year can have extremely large effects on sports success, especially at elite levels. The discovery of the RAE in children's sports came as the result of an analysis of the birthdays of professional ice hockey players in Canada. Barnsley, Thompson, and Barnsley (1985) found that these players were much more likely to have been born early in the calendar year than in later months. First quarter birthdays were twice as common as last quarter birthdays.
In a follow-up study it was found that the RAE was even greater among elite youth teams (Barnsley & Thompson, 1988). In the case of 9- and 10-year--olds, almost 70% of the top players were born in the first half of the year. More striking was the fact that only 10% had birthdays in the last quarter of the year. Interestingly, the RAE was not evident in professional ice hockey in the 1960s (Daniel & Janssen, 1987). This might suggest that the regimentation and sophistication of youth hockey in recent decades may be a factor in producing the RAE.
Once the RAE in sports was discovered, numerous researchers investigated the effect in various sports around the world. An excellent review of that body of research may be found in the work of Musch and Grondin (2001). Their review presents evidence of a strong RAE in soccer, ice hockey, swimming, and tennis.
The evidence for a strong RAE in international and professional soccer is overwhelming (Musch & Grondin, 2001). Professional players in the United Kingdom, Belgium, Australia, Brazil, France, Netherlands, Germany, and Japan are more likely to have a birthday in the first half of the soccer year than in the second half. The percent of players with birthdays in the first half of the soccer year is near 60 in most studies.
The data for elite youth players in Europe reveal an even stronger RAE (Musch & Grondin, 2001). Studies of players in the United Kingdom, Sweden, and Belgium found approximately 70% of elite youth players had birthdays in the first half of the soccer year. A literature review of the various factors relevant to the early identification of soccer talent by Williams and Reilly (2000) makes it very clear that advanced physical maturation and stature are extremely important in the selection of elite youth soccer players. Children born early in the selection year are greatly advantaged. These authors also note a "residual bias" that accrues from being selected very early in this process. The theoretical underpinnings of the RAE may be found in the concepts of developmental advantage, socialization, and self-fulfilling prophecy. In the initial stages of the selection of young athletes, a 6 to 12 month developmental advantage can be decisive. Slightly older participants tend to possess physical and psychological advantages that make their selection more likely. Once young players are selected for elite sport participation, they are taught the correct skills and techniques, while being socialized into appropriate attitudes for later success by capable coaches. This specialized socialization process is not experienced by players not selected for elite teams. The absence of this early experience puts younger players who were not initially selected at risk of non-selection at subsequent player evaluations. …