‘What did you do to live this long?’ Survivorship bias shows how centenarians could be outliers

It’s a cliche of reporting on people who reach 100 years of age, or even 110, to ask them some variation of the question: “What did you do to live this long?”

Inevitably, some interesting and unexpected answer is highlighted. Fish and chips every Friday. Drinking a glass of strong liquor every day. Bacon for breakfast every morning. Wine and chocolate.

While a popular news story, this is a relatively meaningless question that doesn’t help us understand why certain people have lived so long. Let me try to explain why, via beautiful buildings, fighter pilots and statistics.

In the second world war, Allied statisticians were applying their skills to minimising the number of bombers being shot down by enemy fire. By studying the damage patterns of bombers returning from action, maps could be drawn up of the most frequently damaged parts of aeroplanes so that expensive, heavy armour could be added to these areas.

Simple enough, right? Then, along comes statistician Abraham Wald who argues for the exact opposite point. The planes that they’re studying are all those that did return from combat with extensive damage, but what about those that didn’t return?

Wald argues that armour should be added to those places that are undamaged on all the returning planes, as any plane hit in these undamaged...

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