Youth sport sorts children into age groups by a , which means a child born just after it competes against children up to a year older. The is the resulting skew in who gets selected. It is well documented in elite male soccer and the female evidence has been thin and contradictory. So the birthdates of 680 female and 1,083 male players in top German leagues were checked.
The skew is there for both, and larger in the men. A statistically significant relative age effect appeared across all players for both sexes, with small effect sizes, driven by an over-representation of players born at the beginning of the year. The effect was more pronounced in German male soccer, significant in both of the top two leagues, while among women it was more pronounced in the second league.
The relative age effect is associated with advantages and disadvantages in competitive sport. Children are grouped by a cut-off date, so a player born just after it may compete for years against peers nearly a year older, and that difference in maturity gets selected for. In elite male soccer the result is a well-documented skew in birthdate distribution.
The female side of the literature is weaker, affected by small samples and conflicting results, which is the gap this study addresses. The sample comprised 680 female and 1,083 male players from the two top German leagues during the 2019 to 2020 season, along with German national teams from the A-team down to under nineteens.
Differences between observed and were analyzed using chi-square statistics and effect sizes, followed by . A statistically significant relative age effect appeared across all players for both sexes, with small effect sizes, and it was driven by an over-representation of players born at the beginning of the year.
By sex and competition level the picture differs. The effect was more pronounced in German male soccer, reaching significance in both the first and second leagues. Among women it was more pronounced in the second league. Keep two limits in view: the effect sizes are small, and a snapshot of who is in a squad says nothing directly about the late-born players who were filtered out years earlier.
wat. Elite German squads hold too many players born in January and too few born in December, in the men’s game more than the women’s.
wat wat
It is a selection artifact rather than a talent signal. A system that keeps promoting the physically oldest child in each year group is losing the late-born players it never looked at twice.
How do we know?
Götze and Hoppe compared observed against expected birthdate distributions for 680 female and 1,083 male players in the two top German leagues and in German national teams. The tools were chi-square statistics, effect sizes and odds ratios.
What is still unknown
Effect sizes were small, and this is a snapshot of one season in one country. The design shows a skew in who is present and cannot show what happened to the players who were never selected.
Learn something?
Where to next
Can an advertisement sliding behind the goal move a penalty kick as well?soccer
Should a goalkeeper facing a penalty really just stay in the middle?soccer
What does it cost to change your mind at the last instant of a penalty kick?soccer