Relative Age Effect. How Birth Month Matters.

by Satyajit Sadanandan | July 8, 2019
Powerful Secrets To Maximize Your Child's Soccer Talent

Myth:  Birth month is not important in soccer selections. 

Fact:   Players born in the first half of the year have an advantage.

Did you know that 38% of the Indian team in the FIFA U17 World Cup were born in January?

Or that 73% of the team players (15 out of 21) were born in the first six months (January-June)?

Ideally, players should have an equal chance regardless of the birth month. But it is not so.

And this is not limited to India. It is fairly common in youth soccer globally as you can see from the graphical data of some of the successful teams in the 2017 FIFA U17 World Cup.

This is also not limited to this U17 World Cup. Research done on the U17 World Cups from 1997 to 2007 showed that 40% of all players were born in the first quarter (Jan-March) and only 16% were born in the last quarter (Oct-Dec).

Players born in earlier months have an advantage due to within-age-group maturity differences. This is known as the ‘Relative Age Effect’.

There is extensive research in many other disciplines — both education and sports — that provides evidence of this effect. It is also not a new discovery. It was first reported over two decades back in Canadian Ice Hockey. But it continues to deeply influence player selections and development in many sports including soccer.

Young players who benefit from it also struggle later on as their physical advantage disappears among grown-ups. So Relative Age Effect negatively impacts everybody.

Here we explore why the Relative Age Effect is so prevalent in youth soccer, why you need to be aware of it and how can you reduce its impact on Your Child.

Why Certain Birth Months Have An Advantage?

Youth soccer selections are usually based on ‘cut-off date’ for any given age group. Most countries follow the FIFA tournaments criterion – based on the calendar year (1st January to 31st December).

But physical development varies among young players. Even among those who are born in the same year but separated by a few months at birth. Older players are more mature than younger players – physically (strength, speed, agility, stamina…) and cognitively (attention, memory…).

At the age of six, a player born in January is about 16% older than one born in December of the same year. At older ages, though this difference reduces in percentage terms, the rapid biological growth rates tend to bring about a huge difference between those players, particularly but not limited to strength and speed. These maturity gaps cause performance gaps that in turn lead to:

  • Selection bias: to a team and within the team (starting lineup).
  • Lesser match experience (for younger players) resulting in a negative cycle – Golem effect.
  • Coaching bias: more attention to stronger/faster players who seem to be ‘naturally talented’.
  • Greater attention leads to better performance cycle among those players – Pygmalion effect.

Even though Relative Age Effect is initially caused by a pure maturity gap, wrong practices in selection and coaching magnify its impact and ensure its continuity into professional soccer.

The following two tables illustrate the impact of Relative Age Effect in the youth teams of the iconic São Paolo Futebol Club in Brazil from a study done in 2011. Out of 341 youth players, approximately 50% were born in the first quarter while only about 10% were born in the last quarter of any given year.

Long-term Impact Of Relative Age Effect

There are many long-lasting consequences of the Relative Age Effect that extend to professional soccer careers including selection to teams and even salary differences among players.

Research on Italian footballers in Serie A showed significant salary differences between those born in the first quarter of any given year to those born in the last quarter of the same year.

In a ten-year study (2000-01 to 2010-11) of 9000 professional footballers across ten European professional leagues, approximately 30% players were born in the first quarter while only 19% were born in the last quarter. Ideally, these figures should be 25% each.

Paradoxically youth players who benefit from their relative age also struggle later to turn professional – as their physical advantage disappears among grown-ups. So Relative Age Effect impacts everybody.

How Can This Effect Be Minimized?

A lot of research has been done over the years on Relative Age Effect in soccer. However, it remains a persistent problem – as is evident. This needs to be addressed at the policy level by FIFA, National Soccer Associations, Clubs and Soccer Academies.

One of the best ways to change it is through ‘Bio Banding’ – grouping players according to their biological age rather than chronological age. It ensures that young players with similar physical maturity are training together. This concept is gaining more acceptance in recent times and organizations including US Soccer and Premier League are trying to implement it.

But this comes with its own sets of challenges.

a. Medical – since there is no perfect method yet to determine the exact biological age.

  • MRI bone scan and TW3 bone test are commonly used but their margin of error is a few months – which defeats the purpose.

b. National team Selections – can’t be through bio banding unless FIFA makes it policy.

Smaller age-gaps in training groups – semiannual instead of annual or biannual – could also work for younger ages. But this is much harder to implement in practice given the age groups in tournaments.

Players born at the end of the year could also be temporarily permitted to change to the age below category instead of the one above (current practice) till a certain age is reached.

How To Reduce The Impact On YOUR Child?

Relative Age Effect may be impacting your child, particularly if the birth month is in the last quarter. For younger ages, physical differences can significantly reduce the confidence of players born in the second half of the year.

If your child is struggling to get selected or losing confidence, pay more attention to the physical differences within the team. The performance difference could be temporary and linked to relative maturity rather than an inherent lack of potential. It is important to highlight this to your child to ensure sustained confidence and motivation.

The best way to reduce the impact on your child is by making sure that your child’s coaches are aware of this problem and factor it in their practice sessions. Good coaches ensure that temporary physical differences in younger ages don’t cloud their judgment of the player’s potential. They won’t pay special attention to players just on the basis of physical superiority.

If the problem persists due to the ignorance of the coaches, explore alternate coaching programs. Ones that are more enlightened and tackle this issue by grouping players based on ability and/or biological age – not chronological age.

Also, explore the possibility of enrolling your child in the next lower age group temporarily. This will ensure that skill development doesn’t get delayed or lost due to late physical maturity.

Powerful Secrets To Maximize Your Child's Soccer Talent
Powerful Secrets To Maximize Your Child's Soccer Talent

2 comments on “Relative Age Effect. How Birth Month Matters.”

  1. That was an eye opener, I was not aware that that month matters! But what troubles me is ,in India they have introduced the TW3 and if physical maturity depends on the month then kids born in the later half are going to miss the bus. Then this actually becomes unfair practice. Of course if a kid does not display ability then obviously he is not going to be selected.but other wise year should be the criteria and not bone tests.

    1. Thank you, Sunil. Will be sharing some thoughts separately on the age tests including the TW3 bone age test - and in general about age cheating - and what parents should be doing. Best wishes!

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