As of today (or as my mother just reminded me, specifically as of 7:30 this evening), I am officially a year away from updating my “About the blogger” page to say that I’m in my early thirties.

So I thought that I’d write a post on birthdays that will sound very familiar to anyone that’s read Malcom Gladwell’s “Outliers”, which I wrote about here.

Accumulative Advantage

So here’s a portion of an infographic that I found:

Some key points:

• At 3 years old, children can vaguely understand the difference between “on” and “under”.
• At 4 years old, children can use basic grammar.
• At 5 years old, children “speak clearly, tell simple stories with full sentences, and carry on conversations using more than 3 sentences”

And if we’re talking about a pre-school class where one toddler is born in January, and another in December, that’s effectively a year’s difference. And when you’re talking about 3 year olds and 4 year olds – the older toddler has had an extra third of the younger child’s learning experiences.

What that means:

• More developed pre-schoolers catch on to things a little quicker.
• So they get a little more attention from the teacher, and slightly better reports.
• Which turns into confidence.
• While the less-developed pre-schoolers get less attention.
• That confidence gets reinforced regularly as the years go on.
• And what was once a small difference becomes a great difference.

And we’re not even talking about the realm of sport – where a few months of age difference can be a dramatic difference in physical development.

Although that’s somewhat mitigated by this:

So admittedly, that’s referring to the US. And it’s also ranking birthdays by popularity (that is: one day may rank higher than another for actual births, but it could differ by 100 births or 100,000 births and this graph would look the same). However, even if you look at the actual birth count, it’s clear that there are more births in August-September than any other time of the year.

Which is to say that the average age in a year group is biased towards being less developed – so the end-of-year babies will tend to be slightly less below-average than an even distribution would imply.

But that’s Northern Hemisphere – and while couples seem to be especially amorous in the winter months (or festive season?) – it’s not clear that would bear out in the Southern Hemisphere.

So I went onto Stats SA, and found this:

So September is still the most popular month for giving birth – suggesting that Christmas season really is the season, regardless of the weather. But winter is also a good time – check out all those January and March babies*.
*February appears unpopular – but then, February also has three fewer days than both January and March. Which would explain some of that difference (even if not all!).

Speaking of the weather

I have one more series of studies that I want to mention – specifically, those that deal with the impact that the season of your birth can have.

Here’s a quote: