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  • William Seah

Survivorship Bias

We love to learn from success stories, especially from people with tried and tested models. These stories of hustling, challenging themselves, changing their lives through different methods intrigue us and inspire us. They challenge us to hope: “if they succeeded, why can’t I?” Often, we tend to attribute their success to their efforts. We emulate them. They took the uncommon path, big risks, and won big.

However, is this always true? Have we asked ourselves, how about ones who have tried using the same method, yet tried and failed? Are these stories worth listening to, and learning from?

I recently read “Fooled by the Winners: How Survivor Biases Deceive Us” written by David Lockwood. The book chronicles different survivorship bias stories, and these made me ponder on the question above.

One of these stories involves airplanes:

During World War Two, the American military wanted to protect their airplanes from being shot down. A fully armoured plane would be too heavy to fly, so they needed to protect only the most critical parts. The military studied the planes that had returned from combat and marked out where the planes were hit the most – wings, the tail, the centre of the plane. They decided to reinforce these areas.
A seemingly wonderful idea; afterall, if bullets were hitting these areas, they should be protected. However, mathematician Abraham Wald realised that they had ignored a critical data set; the planes that did not come back. In fact, these planes that had bullet holes and came back safely showed the opposite of what the military wanted to do. These areas could survive being shot and didn’t need to be reinforced with armour.

Survivorship bias is when we look at the survivors and extrapolate conclusions just from that data set. We ignore relevant data, data from failures.

The people who succeeded, the ones who took uncommon paths, they stand out because they survived. Many others did not.

In Malcolm Gladwell’s, “Outlier”, he talks about success as the result of what sociologists call “Accumulative advantage”. That is, the successful people we hear of have had certain advantages that we don’t hear about. We hear about their work, and granted it was hard work, but we don’t hear about their advantages. Bill Gates was fortunate enough to have gone to a high school which had a computer, back in the time when even colleges didn’t have them. Mark Zuckerberg’s parents were wealthy enough to hire a private computer tutor to come to their house once a week to work with Zuckerberg. Gladwell finds that even your birth year affects your chances of success; depending on when the sport selects its members, typically people born on or around the same time of the year have a better chance at being selected. Certainly, success is very much dependent on effort and not just ‘luck’. But we can’t deny that luck plays a part.

Be careful of survivorship bias. For every success story, we don’t know how much can be attributed to effort, and how much to luck. And because success is broadcasted more than failures, we tend to see the former while ignoring the latter. The survivors are given more attention and it makes us biased towards that data. Emulating successful people doesn’t necessarily lead us to succeed.

The only way to avoid it is to constantly ask what cannot be seen. Consider what data is missing and how it is affecting the conclusion. Recognise that the route to success is never as clear or clean as suggested, and it typically involves a lot of invisible variables.

And in doubt, always remember these famous last words:

“When anyone asks me how I can best describe my experience in nearly forty years at sea, I merely say, uneventful. Of course there have been winter gales, and storms and fog and the like. But in all my experience, I have never been in any accident... or any sort worth speaking about. I have seen but one vessel in distress in all my years at sea. I never saw a wreck and never have been wrecked nor was I ever in any predicament that threatened to end in disaster of any sort.” - E.J Smith, Captain, RMS Titanic

Sometimes, survivors were just lucky. And sometimes, luck runs out.

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