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Why Athletes’ Birthdays Affect Who Goes Pro — And Who Becomes A Star
If you want to be a professional athlete in most sports, it helps to be born at the right time of year. In basketball, baseball and ice hockey, players born in …
fivethirtyeight.com
Why Athletes’ Birthdays Affect Who Goes Pro — And Who Becomes A Star
By Tim WigmoreFiled under Sports Science
If you want to be a professional athlete in most sports, it helps to be born at the right time of year.
In basketball, baseball and ice hockey, players born in the first quarter of their selection year — the cutoff for which age-group teams are picked, which is normally the school year — are overrepresented both in youth and professional sports. In soccer, players born in the first quarter of their selection year are overrepresented throughout major leagues in Europe and South America.
This phenomenon, called the relative age effect, impacts almost every sport. It has been demonstrated in both men’s and women’s sports, although the effect seems to be less pronounced in women’s sports.
Of course, children old for their cohort don’t have better genes or more talent. Instead, “the relative age effect is almost certainly related to differences in rates of biological and psychological maturation,” said Joe Baker, a professor at York University in Toronto who researches the relative age effect. “Those who are relatively older appear stronger, faster, etc., but they’re really just older and therefore more advanced in their maturation.”
Such children are more likely to be picked for school teams. Once they are picked, players benefit from more practice, coaching and game time — advantages denied to those not selected, who are disproportionately likely to be younger for their selection year. Once accounting for their biological age, the older players might not have been any better than later-born children when they are first picked. But after becoming part of a team, and being exposed to training and matches, they really do become better than later-born children who might be equally talented.
One clear trend holds true across sports: The younger that talent is identified, the greater the relative age effect. This makes intuitive sense; on a fourth grade sports team, made up of 9- and 10-year-olds, the oldest child could be 10 percent older than the youngest.
