Have you ever watched the Little League World Series on television? Ever notice how the players on the teams are almost always much bigger and stronger than the average twelve-year-old and look more like sixteen-year-olds?
What you are seeing is a phenomenon called the relative age factor (RAF) at work. As numerous studies have shown, success in age group competition, as is the rule in soccer, swimming, baseball, ice hockey, and tennis, may simply result from a child being lucky enough to have a birth date early in the selection year.
When young athletes are competing for spots on select teams, a six-to twelve-month developmental advantage can be decisive. Slightly older participants are more likely to be selected because they tend to be more mature physically and psychologically. The relative age factor can and often does have an extremely large impact on success in sports, especially at the elite levels. It is a special problem in sports where height, weight, strength, and power are an advantage.
As a 2004 article in the Journal of Sports Behavior argues, "the long-term result of the RAF may be a lowering in the over quality of the highest competitive team" as talented individuals may be overlooked because they are born late in the selection year.
Adapted from Brooke de Lench's book, Home Team Advantage: The Critical Role of Mothers in Youth Sports (HarperCollins 2006).