Benford’s Law
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I’m putting together the results of the Perl Survey, and as I sat on IRC this evening I mentioned that I was collating the data regarding years’ experience in programming.
“I bet,” said Greg McCarroll, “that about 30% of people said they have either 1 year or 10-19 years’ experience.”
I took a look at the figures, and it turns out to be 36%. I was reasonably impressed, but Greg admitted he was just using Benford’s Law. I’d never heard of it before, but apparently it’s a rule that 30% of responses to just about any question with numeric answers will begin with 1. Even more interestingly:
This counter-intuitive result applies to a wide variety of figures, including electricity bills, street addresses, stock prices, population numbers, death rates, lengths of rivers, physical and mathematical constants, and processes described by power laws (which are very common in nature). Even more counter-intuitively, the result holds regardless of the base in which the numbers are expressed, although the exact proportions of course change.
Last time I studied statistics was at secondary school in the early nineties. Makes me wonder what I was thinking when I signed up for this project :-/
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