Do we question the relative age effect enough?

A conversation I’ve been yearning to have with fellow coaches for quite some time; the presence of the relative age effect (RAE) in sport and whether we, as coaches, overly dictate selection based on it.

Luckily enough, the Edge of Play (@EdgeOfPlay) hold a mostly weekly ‘Coaches’ Huddle’ where we discuss a different topic for an hour and we recently spoke about the implications of RAE on our coaching.

I am aware the RAE will be a term some readers might not be aware of, but it’s a phenomenon that’s been highlighted over the last four decades (Barnsley et al., 1985). To put it blankly, the relative age effect refers to the unconscious bias toward selecting players and athletes based on their birthdate (Burgess and Naughton, 2010) due to a physical and cognitive advantage they have over their peers.

Before I provide an example, I must emphasise in the UK (we like being different over here) that we use September-August to categorise age groups as opposed to most other countries where it is determined by January-December.

For instance, a child born in September – at the beginning of their year – are far more likely to be physically mature and superior than a team-mate whom was born in August, almost twelve months later. This is a significant issue for a number of reasons….

Firstly, it’s been identified that RAE bias can lead toward potential learning disabilities and weaker social interaction skills (Fumarco and Baert, 2019), and more importantly, this can have an impact on a child’s life through adolescence and eventually adulthood (Fumarco et al., 2020). Additionally, as an individual doing a degree in sport psychology, it’s also critical to note that this bias toward early birth athletes may leave the younger players with less competitive experience, lower self-esteem and motivation, and a lower chance to receive high-quality training (Musch and Grondin, 2001).

Before people question RAE, it is not just a UK or European phenomenon. Kelly et al. (2020) discovered studies that provided the existence of RAE in Brazil, U.S., UK, France, Germany, Japan, and many others. Although, now I feel like I’ve painted some sort of picture of the relative age effect – the question now lies on whether, if we’re aware of it, are we using RAE wrongly to dictate our coaching or should it just be something coaches are aware of but use it alongside many other components to guide our skillset in the spirit of youth development?

Whilst this is a critical opinion of the RAE, it is important to note the contrasting difference one’s physical growth may be depending on their age. For example, at under-6 level there could be as much as a 15-20% life difference between some players; obviously that percentage distinguishes the older people become until, eventually, there is no difference whatsoever.

With that in mind, do you consider RAE at all? Do you rely on it too heavily when initiating coaching? Those are just two of many questions we, as sport coaches, can ask ourselves in reference to the relative age effect.

I will attempt to answer these sorts of questions in accordance to my opinion. Thus, I must emphasise that this blog is purely my opinion but will be formed on academic understanding of the phenomenon, as we know it.

Firstly, what are the advantages of applying RAE knowledge to our skillset? It enables us to further develop individual development plans (IDPs) even more specifically to the person. McCarthy and Collins (2014) discovered that those born later in the categorised year (i.e., August) are more likely to advance other areas of their development in order to compensate for their physical disadvantage. For instance, those younger individuals were found to grow greater psychological and technical skills (McCarthy and Collins, 2014) than their older peers. The correlation between that and RAE remains inconclusive but we are able to make a fair assumption based on the coincidence.

Obviously, in an ideal world there would be no imbalance just as a consequence of being born in a different part of the year to a team-mate, but that is a situation coaches should be aware of, for certain.

Referring back, is that imbalance a result of coaching intervention or is it just an unconscious coincidence – again, we cannot know for certain. However, given this evidence, I have now become aware of that variance, and am now observing that within my players. Remembering that not every team is the same, younger players potentially having greater technical and psychological skills is not a global, uniform pattern and I strongly encourage other coaches reading this to assess their own group to either prove or disprove that theory.

If players born between June-August (or October-December for those not in the UK) don’t have those psychological and technical advantages, and are struggling with the physical superiority of their peers, then maybe this is something to consider when forming IDPs. Additionally, what is staggering from McCarthy and Collins’ (2014) study – which was within a Rugby Union academy – is that they found those born later in the categorised year, were four times more likely to achieve a senior professional contract. Is this down to their psychological and technical superiority that they’ve been unconsciously forced to develop due to their likely physical disadvantage?

It’s difficult to know, with far too many caveats. We can’t conclude anything from a singular study, which is why I strongly encourage readers to conduct their own research into RAE. Furthermore, the researchers did not take physical measurements for their participants to see if the players conformed to the relative age effect of physical disparity. Therefore, the uncertainties from this particular study make it challenging to assume that RAE has a long-lasting impact up to senior participation, but that is another subject altogether for another day.

In my opinion, coaches can use RAE to inform a section of their coaching and IDPs. It would also be interesting to discuss if coaches observe a superior disparity in skillset between younger and older players. Consequently, it is important for us to be aware of the relative age effect but we should not use it solely to dictate our individual coaching.

As always, thank you for taking the time out of your day to read my blog – it is greatly appreciated. If you would like to reach out to me and discuss this topic further then by all means do so – on Twitter @RyanJ_White99 or email at Stay safe.

Barnsley, R. H., Thompson, A. H., & Barnsley, P. E. (1985). Hockey success and birthdate: The relative age effect. Canadian Association for Health, Physical Education, and Recreation51(1), 23-28.

Burgess, D. J., & Naughton, G. A. (2010). Talent development in adolescent team sports: A review. International journal of sports physiology and performance5(1), 103-116.

Fumarco, L., & Baert, S. (2019). Relative age effect on European adolescents’ social network. Journal of Economic Behavior & Organization168, 318-337.

Fumarco, L., Baert, S., & Sarracino, F. (2020). Younger, dissatisfied, and unhealthy–Relative age in adolescence. Economics & Human Biology37, 100858.

McCarthy, N., & Collins, D. (2014). Initial identification & selection bias versus the eventual confirmation of talent: evidence for the benefits of a rocky road?. Journal of Sports Sciences32(17), 1604-1610.

Musch, J., & Grondin, S. (2001). Unequal competition as an impediment to personal development: A review of the relative age effect in sport. Developmental review21(2), 147-167.

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