The Relative Age Effect in the Chinese National Table Tennis Team

Well, this is a serious sounding post – isn’t it? What on earth does “relative age effect” mean?

Today, I’m taking a break from writing about coaching or equipment to highlight a rather interesting phenomenon in elite sport and demonstrate how we may be able to see it most clearly in the Chinese National Table Tennis Team!

But before I jump straight into it, here’s a brief introduction to the relative age effect.

What is the relative age effect?

This is what Wikipedia has to say for itself…

The term relative age effect is used to describe a bias, evident in the upper echelons of youth sport and academia, where participation is higher amongst those born early in the relevant selection period (and correspondingly lower amongst those born late in the selection period) than would be expected. The selection period is usually the calendar year, the academic year or the sporting season.

The bias results from the common use of age related systems, for organizing youth sports competition and academic cohorts, based on specific cut-off dates to establish eligibility for inclusion. Typically a child born after the cut-off date is included in a cohort and a child born before the cut-off date is excluded from it.

The most commonly used cut-off date for youth international sporting competition is 1 January. The IOC and FIFA both use 1 January as their administrative cut-off date when determining an athlete’s eligibility to compete in youth competitions, children born before a specified cut-off date are excluded.

Cut-off dates for academic cohort structuring, including the setting of academic years, are usually determined by national education authorities and tend to be based on autumn start dates, so August or September cut-off dates are common in the Northern Hemisphere and February or March cut-off dates are common in the Southern Hemisphere.

Malcolm Gladwell’s book Outliers: The Story of Success and SuperFreakonomics by Steven Levitt and Stephen Dubner have popularised the issue in respect of Canadian ice-hockey players, European football players and US Major League baseball players.

So, the gist of it is that children that are relatively older than their peers do better than those that are relatively younger than their peers. That makes sense, I guess. The relative age effect creates an advantage to those born earlier.

Here’s it is in action…


This first chart (above) shows a steady decline in the number of European elite youth football players as the month of birth moves from January (the oldest in the age category) to December (the youngest).

The second chart (below) displays the same phenomenon in the field of academia. Graduates from Oxford University (one of the best universities in the world) were much more likely to be born in September (the beginning of the academic year) than August (the end).


It’s all massively unfair but is simply a side effect of grouping children into 12-month categories. Obviously, the January-born children that are almost a whole year older than the December-born children will be better football players (on average). They are much more developed both physically and mentally.

Applying it to table tennis

I was interested to see if a similar effect could be found in elite table tennis – so what did I do? I went through every player in the men’s top 50 list and found their birthday. Obviously, it’s not the world’s biggest sample but here are my results…

  • January = 8
  • February = 5
  • March = 3
  • April = 5
  • May = 3
  • June = 4
  • July = 2
  • August = 5
  • September = 7
  • October = 7
  • November = 1
  • December = 0

I felt like I had found something. There should have been roughly four players born per month, whereas there were eight born in January and only one born in November and December combined (Do you know who it is? It’s a tricky one!) It certainly wasn’t super clear, though, with quite a big group of players born between August and October.

Then it dawned on me that in many countries the cut-off is probably September 1st. After all, that is what we use in England for our age groups – even though internationally the cut-off is January 1st. Perhaps that could explain the fourteen players born in September and October?

I did all of that right at the end of 2015 and thought I would leave it at that. But then, in early 2016, I discovered something much more interesting!

The Chinese National Team

The relative age effect thrives in an environment where children are selected at a young age and put through a system with an abundance of competition. A great example of this is youth ice hockey in Canada. The problem is, in many countries the standard of youth table tennis just isn’t that high. National coaches don’t have thousands of children to pick from. Sometimes they feel lucky if there are just a couple of kids who look decent and have the potential to make it internationally.

This isn’t the case in China, though. In China, the national pyramid system puts thousands of children on the table tennis excellence pathway, each and every year. The best young players make it up to the next level while the others are rejected. It’s ruthless, but it certainly gets results.

If the relative age effect should be seen in action anywhere, it should be within the Chinese National Table Tennis Team…

…And it is!

#TeamChina Men

As I write this blog post we are about half way through the ITTF Perfect 2016 World Team Table Tennis Championships in Kuala Lumpur. The Chinese men’s team is looking strong (as always) and so far haven’t lost a single individual match – winning all four of their group matches 3-0.

That’s not surprising, their team consists of the world #1, #2, #3, #4, and #10. If they don’t win it will be the biggest upset in sporting history!

However, what is interesting is the birthdays of those five players. You may have already seen them at the top of this post but here they are again…

  • Ma Long: 20th October
  • Fan Zhendong: 22nd January
  • Xu Xin: 8th January
  • Zhang Jike: 16th February
  • Fang Bo: 9th January

Looking at that actually makes me respect Ma Long even more!

Three of the five were born in January (and as such are the oldest in their year) and Zhang Jike was born in the middle of February (still making him one of the oldest players in his year group).

Of course, this could all be a coincidence. After all, five isn’t a particularly large sample size! Let’s look at the Chinese women’s team to see if we find a similar pattern.

But before we do…

  • Liu Guoliang (Men’s Head Coach): 10th January
  • Yan An (China’s #6 and WR15): 12th January

#TeamChina Women

China also has five female players representing them at the World Team Championships. So far they have managed to match the men and win every match 3-0. That’s hardly a surprise, though – all of them are ranked in the top 10 in the world!

What I want to know is if they were all born in January?

  • Liu Shiwen: 12th April
  • Ding Ning: 20th June
  • Zhu Yuling: 10th January
  • Chen Meng: 15th January
  • Li Xiaoxia: 16th January

Once again, three of the five players were born in January. That’s six out of the ten competing for China at the World’s! It’s pretty unbelievable really and blows out of the water any figures reported previously in other sports. But wait. There’s more.

I mentioned earlier that all of the female Chinese players competing in Kuala Lumpur were ranked in the top 10 in the world. Well, China have two other players ranked in the top 20 who didn’t make the cut this time – and they are…

  • Wu Yang (WR10): 5th January
  • Mu Zi (WR15): 9th January

You couldn’t make this stuff up!

To summarise…

  1. China has six male players ranked in the top 20 in the world. Four of them were born in January and one in February.
  2. China has seven female players ranked in the top 20 in the world. Five of them were born in January.
  3. And just for good measure… Liu Guoliang was born in January too!

If it ain’t broke, don’t fix it

China clearly believes that their national pyramid system selects the most talented young players and weeds out the least talented ones. That is probably true, to an extent. But by starting so young and grouping children into strict age groups it also gives a massive advantage to those born in January.

I guess Fan Zhendong is the ultimate relative age effect player. Not only was he born in January but he was also, clearly, an early bloomer/developer in the physical sense. When we first saw him in 2012, aged only 15, he already looked like an U21! He must have made the average December-born 15-year-old Chinese player look like a baby.

How many other potential Ma Long’s have there been who haven’t made it through the system largely due to the fact that they were born in December. I wonder if there are any December-born players in the extended Chinese National Team at all!

It’s interesting that neither of the two best Chinese players (Ma Long who is #1 in the world for the men and Liu Shiwen who is #1 in the women’s) were born in January. Perhaps these two players were so talented and destined for greatness that even a rubbish birthday couldn’t hold them back! You could make the point that China would be even stronger if they managed to identify talented young players who were born later in the year.

However, China continues to dominate our sport of table tennis and I’m sure they will win gold in both the men’s and women’s team event in Kuala Lumpur. Perhaps there is no need for them to change anything. Their early specialization pyramid system is clearly working.

But imagine if they improved their talent identification. Then we’d all be in even bigger trouble!