It basically gets lower and lower throughout the months

I often wonder about this - how birth month might affect academic or sporting performance. Someone must have done this research to some extent, surely? I'm from the UK, had kids in Mexico (where school year cutoff was December at least in our district) and now live in US, where it's October, but where so many parents try to game the system by holding their kids back that some districts are really strict on age/school start dates. It's fascinating.

Or it could be because they're generally the biggest, smartest and most mature of their peer group they develop better confidence and leadership skills and are therefore more likely to pursue things to their highest level.

Or maybe a little from both.

Data from Wikipedia. Image created in Excel. There were a few years with ties in the rankings; for simplicity's sake I ranked them in the order they were presented in the Wikipedia page.

Definition should include motivation.

This is true and I suspect that would explain the spike in September!

This was covered by Malcolm Gladwell in Outliers, except for hockey.

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A minute ago you thought what was really important was the definition they were using. When that was clarified now it's motivation?

Interesting. Expected, but interesting.

In the US (well at least my school district in Minneapolis) it oriented around a school calendar i.e. those born September 2000 to August 2001 were all in the same class. People born in September and October were always the oldest in their class. Long story short this graph and the interpretation of this graph is wrong for a number of geographical and cultural inconsistencies.

It's probably just the fact that September is the most common birth month

Doesn't matter when schools starts, it matters where the age cutoff is. I live in Canada where school starts in September, but you are divided by birth year. Is that not the norm in the Western World?

To my best knowledge tableau is using the area of the circles as the visual variable

Interesting data, but shouldn’t this also be compared to the average birth month pattern in general? That would provide more evidence for the relative age effect. Births are not equal across all months to start with in humans (even simplistically based on days of the moths).

That is not correct, at least in Spain. The classes start on September, but the students go to class following the calendar year. Someone born in April and someone born in November of the same year will go to the same class. And the same for sports.

Here's the data on hockey. https://www.quanthockey.com/nhl/birth-month-totals/nhl-players-career-stats.html

Well, academic year in Poland starts in september but you still go to classes according with year you were born in. Children from January wil be the oldest in class and the ones from December the youngest(There are also cases where a children from example December can be moved to another year)

I'm sorry its not another ugly bar chart like the frontpage of shit sub is. It's okay to actually use your comprehension skills once in a while. There's a lot of brilliant graph types that's not immediately obvious, just pick up any data visualisation book. The point is, once you understand the graph, the visualisation provides a useful tool for your brain to comprehend the graph. The point is not to have the prettiest bar chart because anything else is difficult to understand.

It's interesting, and it kind of works to break it down this way. I didn't fully articulate what my concern is in my other comment, my question is how do you account for situations in which the same person in the same activity would be on opposite ends of the age gap depending on where they play.

A child born late in the year would have the most advantage in school sports, even say just PE class all the way up to the varsity team in high school, but that same individual (particularly as a younger child) would be on the bottom end of the age gap advantage in a city sponsored league that uses the calendar year

Interesting article breaking down just North American sport leagues.

https://www.researchgate.net/publication/290649143_Does_Relative_Age_Affect_Career_Length_in_North_American_Professional_Sports/download

Ahhhhh totally makes sense. Thank you for deepening my understanding of this cool phenomenon.

Same in Canada.

I disagree that it is hard to understand. I think it shows the trends really well actually. Maybe kind of complicated, yes, but I was able to digest it pretty quickly.

I do always have a problem with the size of circles being used to illustrate data since the area of a circle goes as a square, or is the diameter (instead of the area) of the circle correlated to the data?

and The Office

It depends too much on the organization to really be able to split it up for every case.

In the US age /birthday cutoffs vary place to place, but Aug-sept is most common for school classes meaning you are right a child born in September is 10-11 months older than some of their peers in the same class which can be a significant advantage particularly in early years.

Kids' sports (and also many other non sport related extra-circular activities not directly sanctioned by the school) tend to be broken down either by grade, in which case the ~Fall-Late Summer range is most relevant, or by age regardless of grade, in which case Jan-Dec will be the range that matters.