What is the Relative Age Effect?
In football, age groups are determined by calendar year. Someone born in January plays in the same age group as someone born in December – even though there can be up to an 11-month age difference between them.
For a 9-year-old January-born child and an 8-year-1-month-old December-born child, the age difference is over 10% of their life so far. At this age, that's an enormous advantage.
Consequence: The older players in an age group are physically stronger, more coordinated, and cognitively more advanced. Coaches often select them. They receive more playing time, more training, and more self-confidence. They develop faster – not because they are more talented, but because they were nurtured earlier.
Accumulated over years: The advantage grows, it doesn't diminish. Those who are favored in the U11 (E-Jugend) are stronger in U13 (D-Jugend), significantly superior in U15 (C-Jugend), and in a development program in U19 (A-Jugend) – even though the initial advantage was only a few months of life.
The Data Behind It
Studies clearly show the effect:
- In German NLZs (Youth Performance Centers), players born from January to March are approximately 2-3 times more common than those born from October to December.
- In Bundesliga professional squads: a similar distribution.
- In DFB national selections: an even stronger effect.
This is not a random distribution. It is systematic favoritism.
Why the RAE Exists
Three contributing causes:
Cause 1: Physical Maturity
A 9-year-old January-born boy is, on average, 3-5 cm taller than an 8-year-1-month-old December-born boy. He has advantages in duels, heading, and sprinting.
Cause 2: Cognitive Maturity
Game understanding, concentration ability, learning from mistakes – all of this depends on the stage of maturity. Older children in the age group understand instructions faster and make better decisions.
Cause 3: Self-Confidence and Experience
Older children have more life experience. More self-confidence. They are more willing to take risks. They are more present in training and games.
Why the RAE is a Problem
Four consequences:
Consequence 1: True Talent is Overlooked
A highly talented December-born child is overlooked because they appear weaker in direct comparison to an average January-born child. Talent is not discovered; it is filtered out.
Consequence 2: Injustice for the Children
A child who doesn't make it into a development program often stops playing football seriously. Then the talent is lost forever.
Consequence 3: Distortion of the Player Pool
At the highest level, talents who were filtered out due to RAE are missing. German football loses overall quality.
Consequence 4: Self-Reinforcement
Those who are developed early get better. Those who are not developed early fall behind. Over years, the initial birth month difference turns into a huge performance gap.
What You as a Youth Coach Can Specifically Do
Six concrete strategies:
Strategy 1: Assessment in Context
When you evaluate players (in Coach OS or manually), consciously note their birth month. A "6-rated" player born in December might be an "8-rated" player – in a year.
Tip: In Coach OS, you can store the birth month in the player profile. Make it visible during assessments to avoid making unfair comparisons.
Strategy 2: Actively Balance Playing Time
Late birthdays often get less playing time. You can actively counteract this: give December-born players as many minutes as January-born players.
When setting up training and distributing playing time, consciously pay attention to the distribution of birth months.
Strategy 3: Sort 1-on-1 Drills by Maturity Level
In game forms, you can deliberately group players by maturity level. Instead of just "talent vs. talent," also sort "older child vs. older child" and "younger vs. younger."
This gives the younger players in the age group fair conditions to showcase their abilities.
Strategy 4: Multiple Assessment Points
If you only assess once per season, you won't notice who is developing. With three assessments per season (Coach OS standard), you see the speed of development – and can identify December-born players who are rapidly catching up.
Strategy 5: Recommendations for Higher Levels with RAE Mention
If you recommend a player to an NLZ or a scouting tournament, add: "Birth month December, development over the last 12 months above average." This provides the scout with context.
Strategy 6: Educate Parents
Parents often don't understand the RAE. "My child just isn't as good as Tim." You can explain: "Tim is 10 months older. At this age, that's a huge difference."
This relieves pressure from the parent-child relationship.
What Clubs Can Do
At the club level, there are further possibilities:
Measure 1: Bio-Banding
Instead of grouping by calendar year, group by biological maturity. This is practiced in professional football (e.g., at Manchester City): players are temporarily divided into maturity classes instead of age groups.
Difficult to implement in amateur football, but conceivable for individual training phases.
Measure 2: Keep an Eye on Late Bloomers
Clubs should actively look for "late bloomers." Someone who, at 14, doesn't yet have the maturity of a 13-year-old could be a clear top player by 17.
The youth coordinator can keep track of such players via the Coach OS club dashboard.
Measure 3: Multiple Teams, Fluid Transitions
If a club has two teams per age group, players should be able to move between them – depending on their development. This prevents anyone from being fixed in one team for an entire season.
Measure 4: Parent Education as a Club Focus
Parent meetings with the topic "Why your child isn't in the development team" – with an RAE explanation.
What You Should NOT Do
Mistake 1: Denying the Effect
"Our children play regardless of their birth month." Statistically, this is certainly false. You are not immune to RAE effects either – you just need to be aware of them.
Mistake 2: Devaluing Older Children in the Age Group
It's not about disadvantaging January-born children. It's about ensuring fair conditions for everyone.
Mistake 3: Turning December-Born Children into Heroes
Not that either. They are not "better because disadvantaged." They simply deserve the same opportunities.
Mistake 4: Considering the Issue Solved
RAE has been documented for decades but has not diminished. It remains an ongoing challenge.
How to Recognize the Effect in Yourself
Three self-tests:
Test 1: Birth Months of Your Starting Eleven
Write down the birth months of your regular starting lineup. If 70-80% fall within the first half of the year: you have RAE bias.
Test 2: Who Gets Substituted?
Playing time statistics from the last 10 games. Who is frequently brought on, who is substituted? If a pattern by birth month is discernible: RAE.
Test 3: Who Was Recommended for Higher Teams?
If all your recommendations are for players born from January to March: RAE.
If one of these tests is positive, you need to take action. If all are positive, you are part of the system – without intending to be.
How the RAE is Reflected in Professional Football
In Bavaria, at the DFB, and in the Bundesliga, the RAE has been a topic of discussion for years. Some professional clubs have deliberate programs:
- TSG Hoffenheim has actively considered birth months in talent development to balance the effect.
- Manchester City is experimenting with bio-banding.
- DFB training center program is increasingly designed with RAE awareness.
But: The effect is persistent. Without active countermeasures, it remains.
How Coach OS Helps You with RAE Awareness
Coach OS documents birth months in player profiles. You can:
- See the birth month distribution of your starting eleven.
- View assessment histories in the context of the birth month.
- Filter playing time statistics by birth month (in the club dashboard).
This doesn't replace your awareness – but it gives you the data to make fair decisions.
Frequently Asked Questions about the Relative Age Effect
Conclusion: You Can't Solve the RAE Alone – But You Can Stop Reinforcing It
The Relative Age Effect is a systemic problem in youth football. As an individual coach, you cannot eliminate it. But you can stop unconsciously reinforcing it.
Conscious distribution of playing time, fair assessment in the context of birth month, active recommendation of late developers, parent education – these are the levers you have as a coach.
This accumulates over the years. Players you have treated fairly develop differently than if you had written them off after 6 months.
[Try Coach OS for fair player development documentation for 30 days free →](https://coach-os.com)
Coach OS is the platform for football training planning. With player profiles that document birth months and development histories. From Hamburg.