Tim's birthday is on September 29th. He's 7 years old. Tom's birthday is on August, 23rd. He's still only 6 years old. Both of them will attend the first class in primary school this autumn. Why? They are in the same age group. However, there's nearly one year of age difference and as we all know, one year difference means a lot in terms of a cognitive development, particularly during childhood and adolescence.

In most countries and public school systems, a one year age difference is the maximum, and still it is very common. We also call this difference of age in the same age group relative age. In most sports, cut-off dates such as the turn of the year are also applied in order to avoid large age differences and provide fair competition as well as equal opportunities.

What are the consequences and problems of a highly different relative age?

In schools, studies provide evidence that younger pupils have more academic problems than older ones. When starting school at an early age, pupils are more likely to be classified as learning disabled and achieve less than their classmates. Even though these significant differences exist at the start, they level out in the following years. The reason might be that the hard work of younger students pays back later on. Also, "weaker" students might get more attention. This hard work might even lead to superior performances in the long term as academic success is determined by high motivation and persistence rather than by relative age effects.

However, we also know that – compared to school – younger children are more likely to drop out in sports instead of continuing voluntarily. The main difference between sports and school is that school is compulsory, doing sports voluntary.  

What influences the relative age effect?

The more potential athletes for a team, the stronger the relative age effect (RAE) occurs. Let's say there are 10 potential climbers in the Youth B category (under 16) but there are only four open places for competing internationally. As you can see, there will be a strong competition. The RAE is particularly strong in this male category (age 14-15). Obviously, the more popular the sport is, the more likely the RAE occurs because there will be more competition... The RAE in very popular sports such as soccer will always be really strong.

Being successful in a sport requires certain physical capabilities. Our physical capabilities strongly correlate with our chronological age. Fair enough, Tim (from our school example) might be taller and physically more developed than Tom, even though they are in the same age group. In certain situations, e.g. climbing in finals at a bouldering competition, he will have an advantage compared to Tom since he can reach certain holds better and therefore needs less power. He might be taller and more powerful e.g. in doing pull-ups or sit-ups. A disadvantage due to relative age together with a late maturation can make it impossible for young players to compete. 

Another factor that influences the relative age effect is our psychological maturity. Perceived competence is e.g. one important factor for our performance and development. What does this mean? Tim feels competent in climbing (= in a certain activity or domain). This is important because it facilitates reaching his goals (e.g. getting onto the podium in a national competition). Perceiving competence in a certain field is also very satisfying – Tim knows he is good at climbing, he achieves his goals and he knows that if he keeps training, he will just get better at it (if he engages he will effectively improve). The older we become, the more accurate our perceived competence becomes in relation to our actual performance. We are less accurate when we're 8 to 9 years old but become better at the age of 10 to 13. The higher our perceived performance, the more intrinsically motivated we are. Tim really enjoys what he's doing! Why is it important that our actual and perceived competence are similar? Well, if we perceive ourselves as being really competent at something but keep failing at these exact things, we can very easily get really frustrated! This means, athletes with a higher relative age are more likely to continue and enjoy what they are doing and not giving up due to their advantage in their cognitive development.

Last but not least, our experience is influenced by the RAE. Tim is nearly one year older than Tom – which means he had one year more of experience, which means more training. We also know that older athletes are often more likely to be chosen to be on a team...

What can we do to better deal with RAE?

Most importantly, coaches must be fully aware of the RAE and try to make their judgements and decisions on who to take to e.g. international competitions based on the knowledge that there are physical and psychological difference between kids of the same age group.

A possible step could be to look at athletes' technical strength instead of their physical strength. Coaching should be equal to all athletes – independent on their age. It should be encouraging and motivating. A coach should maintain interest and motivation. Being allowed to participate in different competitions are a necessary motivation factor to keep the drop out quote low. 

Last but not least, coaches should rather focus on individual improvement than (unfairly) comparing athletes to older ones of the same age group or focussing on winning.

Have you ever had athletes in your team where you had difficulties in deciding on whether or not to take them to international competitions and where the relative age had an obvious effect on athletes' performances (e.g. in trials)? How did you deal with these situations, what did you learn and what would you do differently today?