Survivorship Bias: What World War II Taught Us About Our Mental Flaws
What survivorship bias is and how it makes you a poor decision maker
July 21, 2019
During World War II, researchers from the Center for Naval Analyses conducted a study on the damage done to returned aircraft after missions. They then recommended adding armor to the areas that showed the most damage to minimize bomber losses to enemy fire.
Wald was a Hungarian mathematician and a member of the Statistical Research Group (SRG), where he applied his statistical skills to various wartime problems.
He noted that the study was only conducted on the aircraft that had survived their missions. It didn’t paint a complete picture when the bombers that had been shot down were not presented for the damage assessment.
With that, the holes in the returning aircraft were areas that need no extra armor — since the bombers could take damage and still return safely. On the other hand, the areas where the returning aircraft were unscathed are those areas that, if hit, would cause the plane to crash and be lost.
Wald then proposed that the Navy reinforce areas by adding more armor to them — which was a perfect demonstration of how to not fall prey into the survivorship bias.
What is survivorship bias?
Survivorship Bias is a logical error that leads to false conclusions by concentrating on the people or things that made it past a particular selection process. And when we do this, we tend to overlook those that got ignored, typically because of their lack of visibility.
It happens a lot in our day-to-day lives and negatively impacts our decision-making. A great example is copying what successful people have done and receiving advice from the so-called gurus and experts:
Bill Gates, Steve Jobs, and Mark Zuckerberg dropped out of college and became wildly successful. But for most college dropouts, it means unemployment and having more immediate student debt.
Messi, Cristiano Ronaldo, and Neymar are getting paid highly as football players. But the truth is, most players never make it into a game in their lifetime.
Motivational gurus talk about following your passion and trusting your gut feelings — but there is no shortage of people who followed their passion and ended up seriously wrong.
When we’re listening to the success stories in any field, we get inspired by the companies, portfolios, and people who made it to the top. What we don’t hear and see are those who tried and failed because generally, people don’t talk about them.
How to avoid falling prey into survivorship bias
Understand the survivorship bias itself helps to prevent it from happening in the first place. When you get clear with what it is, it becomes easier for you to see it again and again everywhere.
The next step is to seek the other part of the story that is missing.
Take “following your passion” as a piece of success advice. We first look at successful people who have followed their passions — and indeed, they accomplished what they desired at the end of the day. However, you need to ask ONE other question:
Did people fail because of not following their passions?
If the answer is yes, then we can come to the conclusion that “following your passion” is the key characteristic to accomplish success.
However, the truth is that there are a lot of people who followed their passions and yet failed. This simple question forces us to look at both positive and negative evidence — and only make our assumption certain when there is no way to prove otherwise.
Seeing the full picture
Being aware of survivorship bias and knowing how to avoid falling into it comes with massive upsides. On the surface, it helps you see through the incomplete information others provide intentionally.
But ultimately, it saves you from wasted resources like time and money by helping you to reach a good, well-informed decision. If making better decisions is important to you, you can check out more about it in my articles on mental models and cognitive errors.