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Birthday distribution – Middle-east edition December 10, 2007

Posted by Sharath Rao in statistics.
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Followup to the previous birthday post:

Luciferratic, a commenter on therandomizer’s blog ( am seriously getting pissed with these pseudonames 🙂 ) has access to a much larger dataset (<raises his eyebrows>). And something looks fishy/interesting. Over 20% of the folks born in the one month – January !!

Update: And fishy it was ! Here is an update on that January-mystery from Luciferatic in the comments section here.

….there definitely is something wrong as the birth rates cannot be skewed to this extent and I have been asking around. This is the first time anyone has tried to look at the portfolio on the basis of month of birth as it really has no relation to the risk profile of a customer.

So, I asked around as to possible reasons as to why the data could be so skewed. Apparently the data is correct, its the birth DATES that are wrong. And I DO apologize about this as I should have checked before posting such a reckless response.

The country I reside in has had a national identification system in place only since 1950. Prior to that there was no official document used to identify birth dates! When the National ID came into play in 1950 most people didn’t know which month they were born in and they were randomly assigned dates in January more often than not the 1st of January! Yes I know it sounds stupid, but prior to 1950, people here were familiar with the Islamic Calendar (Hijri Calendar) and were not used to the Gregorian Calendar. A market norm is to use the date of birth as appearing on the National ID and the result as you have already seen is the data is skewed towards January for customers that were born before 1950.

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