There’s a bloke in my office who has a mild obsession with the theory that the number of deaths in Manchester’s canals over the six years could be down to an undiscovered serial killer. I was a little sceptical of the idea – 61 deaths in canals over a six-year period sounds a lot, and it’s certainly 61 too many – but it’s not such a huge number that I might think it remarkable.
In the 23rd January 2015 episode of More or Less on Radio4 (it’s about two-thirds of the way through, at minutes 18:13 to 23.22), Tim Harford covers the actual likelihood of this being the case – compared to the number of bodies you might expect to fish out of the canal during a typical period of time.
So is there a serial killer at work? Only if they’re also a damn good statistician, it seems.