In life, we rarely talk about the “losers.” Newspapers don’t report on what didn’t happen, influencers don’t talk about the times they failed, and no one writes deep analysis on all the companies that quickly went bankrupt.
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| Photo by Kenny Eliason on Unsplash |
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This is because of survivorship bias. We focus on what we can see (the winners), and ignore what we can’t see (the losers). And it seriously distorts our ability to calculate the odds of something happening.
Why don't we dismiss this survivorship bias thing? One of the reasons is that it makes you feel good, because you too can become another Bill Gates or Mark Zuckerberg who, one day decided to drop out of school and later become billionaires!
One of the most popular stories of survivorship bias played out during World War II and involves a mathematician named Abraham Wald.
During the war, American Bombers were getting hammered by German counter-air defence. The U.S. military was wondering how they could improve the survivability rate of their bombers.
In other words, where could they reinforce their planes to make them more robust to damage? Now, you might say:
Why didn't they reinforce the whole plane?
The answer is simpler than it seems: If the military had protected the whole plane, it would have been too heavy to fly well.
And they had data they could use to make their decision. Here’s an image of the damage the planes took that survived to return to American bases:
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| photo credit Martin Grandjean |
Again, you might say:
You don't need to be a scientist or a mathematician to know immediately where you should reinforce the planes. Just look at the picture!
Well, this isn't what Abraham Wald thought. He took a long look at the damage the planes had taken and did something unexpected: he told them to concentrate on what they couldn't see, and what they couldn't see is all the planes that didn't make it to the base. What was their damage and where was it?
In other words, the picture above doesn't tell you where to reinforce the plane - the bullet holes indicate the areas a plane could be hit and still keep flying - exactly the areas that don't need reinforcing.
Once you are familiar with the idea of survivorship bias, you can start spotting it everywhere.
Can you think of some of the examples?
