You could have become an athlete if you had been born on a different day. What is Relative Age Effect?

What makes a promising child from a local sports club a world football champion, an Olympic medalist, or a Stanley Cup winner?

Some will answer talent. You won’t get far without talent. By the age of five, Tiger Woods appeared in a major golf magazine and on several television shows, and Michael Phelps reached the final of the 2000 Olympics at fifteen. ¹. Others will call hard work. And they will be right too.

But what if there is another reason. Another filter we haven’t heard of before. Or didn’t want to hear. What if it’s not so melodic, not so romantic, and doesn’t fit our idea of ​​true success at all?

Relative Age Effect (or Relative Age Effect)

What is the probability of being born on the first of January? And the tenth of October? Ah… In fact, this probability is fairly evenly distributed throughout the year. However, upon closer examination of birthdays professional football players of the European youth teamseverything turns out to be far from being so transparent.

Birth months of under-19 players (orange) vs. expected (blue)
Birth months of under-19 players (orange) vs. expected (blue)

40% of players were born in the first three months of the year, in the last three – only 12%. — The reason is the trivial division of children into teams according to age.

The first thing a sports school does when meeting a child is to assign him to a team according to the year of birth: team born in 1997, born in 2005, born in 2010. etc. Thus, children born in the same year are in direct competition with each other. For a place in the squad. For the attention of the coach. For the opportunity to represent the school in competitions.

However few months difference at such a young age not just essential, it is critical. A child born in February 2015 is, on average, more developed than one born in November of the same year. It is not only about physical development, but also about mental. The extra nine months of childhood experience simply makes the difference. And coaches, whether they realize it or not, mistake age for talent, physiology and all the other qualities that it is customary to cherish successful athletes.

As a result, these children get more playing time, better training, better development environmentand the snowball of benefits is only growing, turning from a few months of benefits into a qualitative gap in skills.

Or maybe talent really depends on the month of birth?

Of course, horoscopes and astrology can argue with my position, but, in this case, the date of birth does not affect the level of talent or diligence at all. And this is evidenced by at least two facts:

  1. The distribution of “popular” months of birth is different for different selection systems: division by year; selection based on the test; …

  2. Smoothing effect when growing up

About the second in more detail. In favor of the existence of the phenomenon is its leveling over time. When moving from the U19 team to the U21 team, the share of births in the first three months decreases by 5% (39% -> 34%).

Birth months of under-21 players (orange) versus expected (blue)
Birth months of under-21 players (orange) versus expected (blue)

We make one more step towards a full-fledged national team, and again decline. Moreover, the proportion of those born in the last three months is growing significantly. Smoothing is visible to the naked eye.

Birth months of senior internationals (orange) versus expected (blue)
Birth months of senior internationals (orange) versus expected (blue)

Final test. Parse dates of birth the coolestfootballers. As a metric coolness use their transfer value. Voila! Before the eyes even more smoothed distribution. In other words, the colossal skew of birthdays in youth teams is simply not related to the real talent of the players.

Months of birth of the 500 most valuable football players (yellow) vs. expected figure (blue)
Months of birth of the 500 most valuable football players (yellow) vs. expected figure (blue)

Bonus. Take a look at the birth months of the six most valuable footballers right now ²:

🇳🇴 Erling Holland — July
🇫🇷 Kylian Mbappe —
December
🇧🇷 Vinicius Junior — July
🏴————————————————- Phil Foden May
🏴——————————— Jude Bellingham – June
🇪🇸 Pedri – November

And what can be done about it?

There are several approaches to, if not eradicate, then at least reduce the Relative Age Effect:

  • group children into sections with less granularity: team Jan 2015 – Mar 2015; team Apr 2015 – Jul 2015; …

  • use quotas for the number of places in the team by months of birth or comply with the required maximum value of the average age within the team

  • in some sports, to weigh the points of the participants according to their relative age within the year of birth

However, in the context of reality, it is important that none of themby and large, not used on any significant scale. And it’s scary.

Final

In fact, the problem of Relative Age is much more global than sports. It is observed in education (due to a single date for passing exams), and in a career, and in many other areas directly related to competition. ³.

But, if you take something away from this article, it’s definitely something that you should not give up if you were born in December. And, of course, you do not need to predict the conception of a child in order to give birth to him at the beginning of the year. There will be those. Remember that for every distorted selection system there is a Mbappe.

And remember that failures in system design, even the most everyday ones, are all around us. How many potential LeBron James and Leo Messi are the world missing out on for this reason? Maybe you should stop being blind to problems and start experimenting. Test. Make mistakes. But move, move towards a better world.

PS: The author of the article was born in January. And even this did not help him become a football player.


Even more fascinating statistics and research in my cart: @halftimestat. Enjoy!

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