The Relative Age Effect (RAE) is a silent gatekeeper in football, shaping the careers of young players in ways they may never realize. By the time a child enters an academy, their birth month has already influenced their chances of selection, training quality, and long-term development. But the real impact of this bias doesn’t just stop at youth level—it follows players into their professional careers, determining who rises to the top and who fades away.

So, what happens to those who are overlooked? And why is it so difficult for late-born players to catch up, even when they have just as much talent?

The Matthew Effect: How Small Advantages Become Huge

One of the most fascinating (and frustrating) aspects of the Relative Age Effect is how a small early advantage snowballs into a career-defining gap. This concept is known as the Matthew Effect, a term coined by sociologist Robert Merton, which essentially means: "The rich get richer, and the poor get poorer."

In football, this translates to:

• The players who are bigger and stronger at a young age get selected for elite academies.
• Because they play at higher levels, they get better coaching, more competitive matches, and better resources.
• As they develop, they improve faster than their peers—not necessarily because they’re more talented, but because they were placed in a superior development system from the start.

By the time they reach professional age, they’ve accumulated years of elite training and experience, while late-born players have struggled to even stay in the system.
This is why January-born players dominate football academies and why so few December-born players make it to the highest level. The system isn’t just favoring early-born players—it’s actively shutting out late-born talent before it even has a chance to develop.

Survival of the Fittest: Why Late-Born Players Struggle to Catch Up

At first glance, you might think: “Okay, but late-born players will eventually catch up, right?” After all, a 10-month age gap means nothing once players reach their 20s.

But here’s the problem: by the time late-born players physically catch up, they’ve already lost years of elite training.

Most youth academies follow a brutal selection process. Players are constantly evaluated, promoted, or cut from the system. If a late-born player hasn’t physically developed as fast as his early-born peers, he’s likely to be dropped from the academy before he even has a chance to prove himself.

And even if he survives, the opportunities given to him are often far less than those given to his early-born teammates.

Imagine two players, one born in January and the other in December, entering an academy at age 10.

• The January-born player is bigger, stronger, and looks more “ready.”
• He gets more game time, more attention from coaches, and plays in the best youth tournaments.
• By 16, he’s had years of elite-level football, facing top competition week after week.
  Meanwhile, the December-born player has spent most of his career playing fewer minutes, often in weaker teams, because he was seen as a "late developer." By the time he catches up physically, he’s already been left behind in experience, confidence, and tactical awareness.

This is why catching up isn’t as simple as waiting for puberty—the real damage happens long before that.

How This Affects the Professional Game

By the time players reach the senior level, the impact of the Relative Age Effect is still visible.

A 2019 study on European leagues found that:

• More than 50% of professional players were born in the first half of the year.
• Less than 20% were born in the final quarter.
• In some youth competitions, players born in December were almost non-existent.
  This means that professional football is largely made up of players who were given early opportunities, while late-born talents either had to fight twice as hard or never got a chance at all.

The Psychological Impact: Confidence vs. Doubt

It’s not just about physical advantages—confidence plays a huge role in development.

A player who is selected for an elite academy at age 10 grows up believing he belongs at the top level. He receives constant reinforcement that he’s talented, important, and worth investing in.

On the other hand, a player who is overlooked or placed in a weaker team internalizes doubt. Even if he has the same potential, he is constantly reminded that he is “not good enough.” Over time, this affects his self-belief, performance, and willingness to take risks on the pitch.

Many late-born players quit football altogether because they never feel like they’re given a real chance. The sport that once felt like a dream turns into a frustrating, uphill battle where the odds are stacked against them from the start.

The Few Who Beat the Odds

Despite the overwhelming bias, some late-born players do make it to the top. But their journey is often much harder.

Some of the biggest names in football, like Lionel Messi (June), Kylian Mbappé (December), and Luka Modrić (September), were late-born players who had to overcome extra challenges to succeed.

• Messi, for example, was not only born in the second half of the year but also had a growth hormone deficiency. Without Barcelona’s special investment in his development, he might never have become the player he is today.
• Mbappé was physically behind his peers during his youth but was given extra training and mentorship to bridge the gap.
• Modrić was ignored by top clubs for years because of his size before proving himself in the Croatian league.
  These cases show that late-born players can succeed—but they often require extraordinary effort, special circumstances, or pure luck to break through the system that favors early-born players.

In Conclusion

The Relative Age Effect is not just an issue at youth level—it defines entire careers. The players who get an early advantage don’t just start ahead; they stay ahead due to better coaching, more experience, and greater confidence. Meanwhile, late-born players often struggle to even stay in the system, let alone reach the top.

But is there a way to fix this? Can football create a fairer system that allows all talents to flourish, regardless of birth month?

In Part 4, we’ll explore possible solutions—and how some countries are already fighting back against the unseen bias in football development.

Sources

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Do Guys Keep Growing Until Age 25?
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Relative Age Effect
How important is the birth date in football players’ sports career?
Malcolm Gladwell: Full Exclusive Interview - No Small Endeavor
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How a footballer’s birth month can affect their chances of reaching the top
Study reveals birth month impact on soccer careers
Relative age effect:a serious problem in football
The relative age effect is larger in Italian soccer top-level youth categories and smaller in Serie A
Matthew Effect | Definition & Application
Belgium are much more than a golden generation and it is not luck
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“Is early reliable TID possible? No. Is it necessary? No, it is not.” - Prof Dr Arne Güllich