Why averages don’t add up

I recently learned from a doctor friend that salt isn’t necessarily bad for you. Yes, there is a minority whose blood pressure isdriven haywire by eating the stuff, but most people can consume it without much risk. The reason we are formally advised to avoid salt is that lowering salt consumption improves public health on average: salt reduction is helpful to the few who are affected, while being generally harmless for everyone else.

This makes sense at first. Except it leads to a problem. Because if you demonise every food that is harmful only to a minority, you risk recommending so many dietary restrictions that life becomes intolerable. A better answer may lie in personalised medicine: ‘In your case, I’d concentrate on avoiding three things first.’

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James Snell

The slogan that could doom Mark Carney

The notion that any solution which is good on average must also be good overall is dangerously plausible, but often wrong.