Gold Medal Birthday – 23 March

Gold Medal Birthday Bonanza.

Among all the headline grabbing Olympic statistics from the past two weeks, you can’t have missed this one. GB’s four most successful male Olympians were all born 23 March. Amazing isn’t it?

Sir Steve Redgrave, Sir Chris Hoy, Mo Farah and Jason Kenny all get Happy Birthday sung to them on the same day.

It’s generated many articles suggesting that there must be some significance to what seems too incredible a coincidence. And last week Peter Allen, host of BBC’s 5live afternoon radio show, invited listeners to call in with their own stories of personal success relating to that auspicious birthday.

One gentleman suggested that, like the Olympians and others born under the star sign of Aries, he was a determined and successful individual. A mother expressed regret that her daughter, born on that date, was a gifted athlete who wasn’t spotted and slipped through the net. If only someone had realised the significance of her birthday?

Well perhaps that is the case. I can’t prove otherwise.

But, Sir Chris Hoy won his first gold in 2004 and next up was Jason Kenny in 2008. So, until 2008, March 23 wouldn’t have been seen as a trend setting birthday.

Then there is the question of how likely shared birthdays are anyway.


Britain's four leading male olympians and their medals
Sir Steve Redgrave, Sir Chris Hoy, Mo Farah and Jason Kenny. All born on the 23 March – but, is this really that unlikely?

 Sharing a birthday – what’s the chance of that?

In fairness to Peter Allen, he did have a statistician on the show briefly, who explained what’s known as the ‘birthday effect’. I’ve written about that before here. It demonstates how many people you need in a group so that the chance of two sharing a birthday is 50%.

And it’s a surprisingly small number. You only need a group of 23 people.

You can show this using a mathematical equation, but there is another way which is easier to understand. Using a spreadsheet and a small algorithm it’s possible to create multiple groups of 23 people, all with random birthdays and check the results.

So, I created 1000 groups and, as expected, in almost exactly 50% of them two or more people shared a birthday.

And we can use the same ‘monte-carlo’ technique of trial and error to look at birthdays in thousands of much larger groups and compare them with real life examples – such as a team of Olympic athletes.


Team GB

Team GB sent a group of 366 athletes to Rio, which is a rather convenient number since that’s just one more athlete than there are days in the year.

And I’ve compared their birthdays with those generated by 1000 separate trials . Each trial is the same size as Team GB and contains 366 randomly generated birthdays.

Now, you might expect that the birthdays would be evenly spread over the 365 days of the year without much repetition for both Team GB and the 1000 random trials. But, that’s not the case.

Here are the answers to some obvious questions comparing the two groups.


On how many days of the year does no-one have a birthday?

On over a third of the days in the year, 134, no-one in Team GB has a birthday. That is exactly the same as the average of the 1000 random groups of the same size.


How many share a birthday with, at least, one other member of the group?

For Team GB the answer is 63%, which is again exactly the same as the average of the 1000 trials.


On how many dates do three people share a birthday?

There are 18 dates where three members of Team GB share a birthday. In the trial group there is an average of just over 22.


On how many dates do four people share a birthday?

Now this is a bit unusual, there are 11 dates on which four people in Team GB share a birthday. That’s much higher than the trial average of just under 6. In only 7% of trials were there 11 dates generated.

The actual 11 Team GB dates are – 30th Jan, 13th Feb, 12th March, 23rd March, 24th April, 9th May, 20th May, 21st May, 19th Sep, 6th Oct and 30th Dec.

(NB There are no dates on which five athletes in Team GB share a birthday, theoretically there would be one.)


How successful were those eleven groups of current Team GB athletes?

You’ll know that the four born on 23rd March were the most successful as it includes Mo Farah and Jason Kenny. The others born on that day are Tom Farrell who was competing with Mo in the 5k metres and Katie Clark, Synchronised Swimming.

On eight of the other dates the athletes earned at least one gold medal between them.


Fools gold?

Hopefully, from the above you can see that shared birthdays in large groups are far more likely than you might have imagined beforehand.

The only part of the analysis of Team GB that seems particularly unusual is the weighting of birthdays towards the earlier part of the year. This is consistent with some academic studies relating to sports. However, in itself it isn’t that meaningful.

It’s also very easy to get caught up looking for patterns that in reality aren’t there. In other words, there isn’t a reason for the pattern or trend as they’ve been generated randomly. Nassin Taleb wrote a book, ‘Fooled by Randomness’ that explains how serious this is in relation to financial markets. From managing risk to spotting fraudulent activity it’s a major issue.


Data mining

There’s also the problem of ‘data-mining’, which is looking for data which fits your argument.

If I look at a separate group of the top 366 Olympians of all time, the most successful shared birthday IS the 23rd March. There are five birthdays on this day, our four greats and a Soviet speed skater born in 1931 called Yevgeny Grishin.

It isn’t amazing that there are five sharing the same birthday. We should expect that in a group of that size. All that is unusual is that four of them are British.

But, I could sort the data differently.

March 23rd is the 82nd day of the year, but in leap years the 82nd day falls on the 22nd March. And if I sort the information using the 82nd day we get a different group. Chris Hoy and Jason Kenny were born in leap years on the 83rd day of the year. While Steve Redgrave, Mo Farah and our Russian speed skater are joined by Alfred Schwarzman. Schwarzman was born in a leap year 22nd March 1912, he was a gymnast representing Nazi Germany who later won the Iron Cross in WW2.

That isn’t quite such an auspicious group, but I deliberately searched for a more negative outcome to make a point.

As another example, there are 910 inmates at HM Prison Belmarsh according to Wikipedia. It’s very likely that six or more share the same birthday – would you see that as significant?

Would you phone Peter Allen if you shared that birthday?



Please remember:

  • past performance is no guide or guarantee of future returns;
  • the value of stock market investments can rise and fall over time, so it is quite possible to get back less than what you put in, depending upon timing;
  • this blog does not constitute financial advice and is provided for general information purposes only.

Missing the high notes – the 500 euro note (again)

The 500 euro note has a habit of going missing.

This blog draws heavily on the original, but also looks at the latest report from the Luxembourg Central Bank.


In June I highlighted a Europol (European Police Office) report on money laundering. ( You might not think that money laundering regulations will touch you, but the FCA requires all IFAs to carry out basic money laundering checks before working with clients )

Europol’s report explains a variety of money laundering methods and criticises the lack of controls within the Eurozone on the reporting and movement of cash. And Europol are especially interested in the use of cash as, to quote them, ‘although all cash is not criminal, all criminals use cash at some stage in the money laundering process’.

And if you’re going to move cash around it helps if you have a note with a large denomination. Nicknamed ‘Bin Ladens’ from the time when we knew he existed but not where, the 500 euro note means that 10 million euros in paper weighs little more than the average airline baggage allowance – 22 kg.

The European Central Bank (ECB) itself estimates that over 300 billion euros of its banknotes are held overseas.  And in June it announced that no new 500 euro notes would be issued after 2018 as they were ‘taking into account concerns that this banknote could facilitate illicit activities’.

It will be interesting to see whether issuance of the largest notes has changed when the main central banks report next year. In recent years, overall eurozone production of ‘Bin Laden’s’ has been growing. But one central bank stands out in particular, the Banque Central du Luxembourg (BCL)

Below is a graphic from the Europol report which shows data from 2012/2013.

Bank of Luxembourg

The top graph highlights the four main issuers of euro bank notes, Germany, Italy, France and Luxembourg. But, the second graph highlights the scale of Luxembourg’s issuance compared to the size of its economy.

As the source for the graphs shows, this information can also be found in the annual report of the BCL itself. And I was interested to see how much issuance has changed in their latest report for 2015, which was not available when I wrote the first blog in June.


500 euro notes even go missing from the BCL annual report.

In the first section on the amount of new cash issuance, the report refers to demand for the largest notes falling. But, in fact, it’s just the percentage rise in issuance that’s falling, the value of the largest notes issued has increased again.

In the previous year’s report the BCL detailed the amount of each euro note produced. They did the same in each of the reports from 2010 – 2013. However, in its latest report for 2015, these statistics are not included.

They have been replaced with statistics for the Eurozone as a whole, which is how they used to report the data prior to 2010. But one has to ask, why the change? They’ve also chosen to only release the report in French the last time I checked.

Perhaps they are especially sensitive now the 500 note will no longer be issued and the reasoning behind that decision. Or it might be the case that a combination of an O-level (yes, I’m that old) in French and Google translate have meant that I’ve completely misinterpreted the report.

This graph from the 2014 report doesn't appear in 2015.
This graph from the 2014 report doesn’t appear in 2015.


A dash for cash.

It should also be remembered that the ECB decision to stop new issuance of the largest note might not all be about preventing money laundering.

Legitimate demand for cash is bound to increase as the European Central Bank pursues a policy of negative interest rates i.e being charged for deposits.  And several regional German banks are already considering holding part of their reserves as cash rather than being charged for holding them directly with the central bank.

The same will be true of general savers if banks there introduce charges for retail customers as they have with the largest corporate customers. All of which negates the effect of negative interest rates in the first place.

For the policy to work as they expect you need to reduce the availability of cash as an alternative store of value whether you’re a private citizen, business, drug baron or leader of an international sporting federation.

Update: An FT article dated 16th August, covers this issue in more depth, ‘Banks look for cheap way to store cash piles as rates go negative’

You can find the BCL’s annual reports here
There are two blogs on the implications of negative interest rates here and here.


Ending on a different high note.

To those of you with a love of music, here’s Mr Les Dawson showing us all how to really hit the top of your vocal range. This is his emotive rendition of ‘Feelings’ – enjoy.

Please remember:

  • past performance is no guide or guarantee of future returns;
  • the value of stock market investments can rise and fall over time, so it is quite possible to get back less than what you put in, depending upon timing;
  • this blog does not constitute financial advice and is provided for general information purposes only.