Sort children by year group and a January child can be stronger, taller and nearly a year more developed than a December child, though both are in the same age category. That difference disappears by adulthood. What does it manage to do before then?
Start a cycle. A scout is not measuring age but performance, so a selection that looks entirely reasonable may be measuring rather than talent. Whoever is picked then gets , more minutes and more attention, and so really does improve more. Years later the gap is real, and it was made in large part by the early decision.
The number everything starts from is simple. With a January , a child born in January and a child born in December land in the same age group nearly a year apart. At ten that is about a tenth of a life, and it shows in height, in strength and in control of the body.
The scout watching them is not measuring age but performance, so what he sees is a better child. The selection looks entirely reasonable, and it may be measuring temporary maturity rather than talent.
From there a cycle begins. Whoever is picked gets better coaching, more minutes and more attention, and so really does improve more. Years later the gap is real, and it was created in large part by the early decision rather than by the potential.
The measurement is a simple comparison: the distribution of birth months among selected athletes against the population. In many youth leagues the gap is pronounced. Some sports try to correct it by sorting on biological maturity. The size of the effect varies by sport, country, age and gender, and it is a statistical description that does not decide any particular child’s fate.
wat. The relative age effect means the first advantage on a team is sometimes a birth month, not talent.
wat wat
A talent identification system can confuse temporary maturity with long-term potential, and so overlook the younger children in the same category.
How do we know?
Reviews and developmental models compare the distribution of birth months among selected athletes against what would be expected with no bias around the cut-off date.
What is still unknown
The size of the effect varies by sport, by country, by age and by gender. It is a statistical description and does not decide the fate of any particular child.
Learn something?