Success in football, like in many other fields, is often credited to talent, hard work, and perseverance. But what if something as arbitrary as your birth month could determine your chances of making it as a professional? This might sound strange, but research suggests that the month you’re born can significantly affect your football career before it even begins.
This phenomenon is known as the Relative Age Effect (RAE)—a bias that gives older kids within an age group a major advantage over their younger peers. It doesn’t just shape who gets picked for youth academies; it influences who becomes a professional player and who gets left behind.
What Is the Relative Age Effect?
Imagine two young footballers: one born in January and the other in December of the same year. On paper, they’re both the same age, but in reality, there’s a nearly 12-month difference in development. For young children, this gap can mean huge differences in physical growth, coordination, and even mental maturity.
In most football academies, age groups are divided by calendar year. That means the January-born player has a full year of extra growth, strength, and experience compared to his December-born teammate. When coaches are scouting for the best young talents, they naturally gravitate towards the bigger, stronger, faster kids—who just so happen to be born earlier in the year.
The result? A massive overrepresentation of early-year births in professional football, while late-born players struggle to even get noticed.
The Numbers Don’t Lie
This isn’t just speculation—multiple studies have proven the Relative Age Effect is real and widespread.
- A 2015 study by CIES Football Observatory analyzed 29,000 players across 31 top European leagues and found that an overwhelming percentage were born in the first quarter of the year (January-March).
- A study on the 2019 UEFA U-17 Championship showed that 44% of all players were born in the first three months of the year, while only 20% were born in the last three months.
- A youth football study in Ireland found that 80% of players in U-13, U-14, and U-15 league finals were born in the first half of the year.
In short, players born in January, February, and March dominate youth football, while those born later in the year have a much harder time making it through the system.
Why Does This Happen?
It’s easy to assume that older kids get picked because they’re simply better. But in reality, their advantage is mostly physical and temporary.
When a coach sees a group of 10-year-olds and has to pick the most promising talents, the January-born kids look taller, stronger, and more coordinated compared to the December-born kids, who are often smaller and less physically developed. Naturally, the bigger kids get selected for the top academies, where they receive better coaching, more competitive matches, and superior training facilities.
This creates a snowball effect:
- Bigger kids get picked.
- They receive better coaching and training.
- They play against stronger competition, which accelerates their development.
- By the time they reach 16 or 17, they’re far ahead of their late-born peers—not because they’re more talented, but because they had more opportunities.
On the flip side, the smaller kids—often the late-born ones—are either ignored or placed in weaker teams with fewer resources. Even if they had just as much potential, they never get the same chances to develop it.
A Self-Fulfilling Prophecy
By the time these young footballers reach their teenage years, the differences that began as a few extra months of growth have turned into career-defining gaps in experience and opportunity.
The January-born player, who was selected for an elite academy at age 10, has now spent years playing against the best competition, receiving top-level coaching, and being groomed for professional football. Meanwhile, the December-born player, who was passed over, has spent years playing at a lower level, without the same training, facilities, or attention from scouts.
By the time they’re both 18, the January-born player is far more likely to be signed by a professional club. Not necessarily because he was always better, but because he was given the chance to become better.
Breaking the Cycle
If football is supposed to be a game of pure talent and hard work, how do we fix a system that unintentionally punishes players based on their birth month?
Some countries and clubs have started addressing the issue. Belgium, for example, introduced the Future Project, which creates shadow teams specifically for late-born players to give them equal opportunities. Others have suggested biological age classification, where kids are grouped by physical and mental maturity rather than by calendar year.
But for now, the Relative Age Effect remains one of the biggest hidden biases in football—one that has shaped the careers of thousands of players, often without them even realizing it.
In Conclusion
The Relative Age Effect is a perfect example of how hidden advantages shape success in football. While talent and hard work are important, the month you’re born can significantly impact the opportunities you receive. Players born in the early months of the year get selected more often, receive better training, and ultimately have a higher chance of making it as professionals.
But what happens to those born later in the year? Are they doomed to miss out, or is there a way for them to fight back?
That’s what we’ll explore in Part 3.
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Outliers Full Book Summary
Do Guys Keep Growing Until Age 25?
Relative Age Effect Among the Best Norwegian Track and Field Athletes of All Time: Comparisons of Explosive and Endurance Events
Relative Age Effect
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Malcolm Gladwell: Full Exclusive Interview - No Small Endeavor
Are European Soccer Players Worth More If They Are Born Early in the Year? Relative Age Effect on Player Market Value
Birth Advantages in Male Italian Soccer: How They Influence Players Youth Career and Their Future Career Status
Maturity-Associated Polygenic Profiles of under 12–16-Compared to under 17–23-Year-Old Male English Academy Football Players
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The relative age effect is larger in Italian soccer top-level youth categories and smaller in Serie A
Matthew Effect | Definition & Application
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The curious tale of the football international nobody ever heard of (because he was born in the wrong month)
“Is early reliable TID possible? No. Is it necessary? No, it is not.” - Prof Dr Arne Güllich