Beating Survivorship Bias for Better Decisions

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What is Survivorship Bias?

Survivorship bias means you will be:

• Focusing only on people or outcomes that made it past some selection criteria
• Overlooking those that failed

You will end up with a distorted view of how things work.

The best example of this is that plane with the red dots from World War 2. It demonstrates the trap survivorship bias poses for us all.

The Allies were losing too many planes to enemy fire. The solution was obvious — just add armour. But armour was heavy and would impact the plane's performance.

Researchers looked at the returning planes. They found more hits per square foot on the wings and fuselage than elsewhere. They recommended adding armour to these areas.

Mathematician Abraham Wald disagreed. He proposed armouring the areas with few or no bullet holes instead.

His logic: The returning planes were able to fly home despite hits to the wings and fuselage.

But planes hit in other areas did not survive. Planes returning without damage in those areas provided evidence the lost planes couldn't. This simple observation changed the way the Allies armoured their planes. It saved many lives and planes too.

As this example highlights, the evidence of what we see isn't the marker for success we think it is.

Those researchers had a distorted view of success. They had fallen for survivorship bias.

Survivorship Bias: Hiding in Plain Sight

Survivorship bias, along with every other cognitive bias is a threat to every decision you make.

Every time you seek external information to guide your next steps, you're at risk of falling for this bias.

Any study of success is going to present you with an incomplete picture of the truth.

Social media, the news, and the internet all compound our increased exposure to this bias too.

Nearly every social media profile tells you how successful they've been. You will see post after post almost teasing you of how great they've been. Of course, they have fallen for a narrative of their creation.

This not only exploits their ego, it also sucks us in too. And then, when you try to replicate their success, you don't have the same outcome.

Our problem today is the vast majority of us are heavy users of social media. And it is here, where you'll find survivorship bias hiding in plain sight.

Check Your Assumptions and Seek Balance

There is no easy fix for this bias. Awareness is the first step. Making assessments? Consciously check your assumptions. Ask yourself:

Am I overly focused on success stories?

Seek data and views encompassing both failures and successes in context. A balanced study covering survivors AND casualties brings sounder conclusions.

Though survivors catch our limited attention, the full picture includes the fallen. Their stories contribute precious lessons too. Widening the lens provides a clearer picture of reality.

I'll leave with a quote from David Mcraney, from the You Are Not So Smart blog:

If you spend your life only learning from survivors, buying books about successful people and poring over the history of companies that shook the planet, your knowledge of the world will be strongly biased and enormously incomplete. As best I can tell, here is the trick: When looking for advice, you should look for what not to do, for what is missing, but don’t expect to find it among the quotes and biographical records of people whose signals rose above the noise. They may have no idea how or if they lucked up.

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Recommended reading:

• How to avoid being duped by survivorship bias

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