Steve Lawrence is a consultant to Cruyff Football and Ajax in the Netherlands. With a Masters in International Sports Management, Steve founded the Football Analytics Lab and is at the forefront of research into the topic of Relative Age Effects. In this article, Steve explains how the Relative Age Effect works and discusses the impact of this phenomenon.
Relative Age Effects have become a well known, if slightly puzzling, phenomenon in youth football where players with birthdates at the beginning of the season have a huge advantage over their teammates born later in the season.
Relative age effects are not confined to football but can be seen across sport, education and childhood development generally. Hundreds of academic papers have been published on relative age, birthdate effects and school entry age effects since the 1930s, but the paper which pinpointed the issue in respect of competitive youth sport was written in 1985 by Barnsley, Thompson & Barnsley and was titled ‘Hockey success and birth-date: The relative age effect.’
A slightly later paper by Barnsley & Thompson in 1988, also about ice-hockey, went on to identify a ‘relative age advantage’ enjoyed by those with early birthdates, a ‘relative age disadvantage’ experienced by those with late birthdates and a ‘relative age difference’ between the two.
It is the ‘relative age difference’ which is the first thing to be clear about. It’s not the absolute birth month or time of year which is important but the proximity of a birthdate to any relevant cut-off date used for grouping children together:
- If a child’s birthday falls before a cut-off date they are excluded from a group.
- If their birthdate falls after the cut-off date they are included in the group.
This banding tends to be on an annual basis, and for academic purposes the cut-off date has historically been set in the autumn – which in the northern hemisphere has meant August or September.
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