Daily Mail gets odds right shock

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The Daily Mail and other papers carried the story about the Banwell family whose third child shares a birthday, February 5th, with two older siblings, and this time they got the odds right at 133,000 to 1!

This example on February 5th was preceded by the Allali family on October 7th 2010, where the Mail got the odds wrong, and the MacKriell family on January 29th 2008 where they got the odds right - see our previous blog. As Ben Goldacre has discussed, around 167,000 third or higher children are born each year in England and Wales - and at least 1 in 135,000 of these should have two older siblings born on the same day (this assumes random birth dates). So we would expect these events to happen with an average gap of less than 12 x 135,000/167,000 = 10 months, or a median of 8 months apart.

I suspect there may have been an unreported case in 2009 - we need some detectives onto this.

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It's probably only newsworthy* if it's exactly the third child, rather than third or higher. 'New baby shares birthday with two of its older siblings, though not with the other two' doesn't quite have the same ring to it. As there are 102,000 third children born each year, that means you'd expect a 'perfect triplet' about four years out of five - which seems to be roughly what we're getting. *That is, deemed newsworthy by editors desperate to fill space quickly and cheaply with soft human interest stories. I don't think it's actually newsworthy myself.

Nice comment, so we expect an average gap of around 15 months, but there will be a lot of variability around this!