Survivorship Bias: The Tale of Forgotten Failures
Farnam Street (Shane Parrish) · 2019
"We systematically overestimate the odds of success because we only see and study the survivors (the Bill Gateses, the Beatles) while the vastly larger number of people who tried the same thing and failed disappear from view entirely — distorting our sense of cause and effect."
Survivorship bias happens when we draw conclusions only from the subset of cases that 'survived' a selection process (successful companies, famous dropout billionaires, planes that made it home) while the failures — often the much larger group — are invisible, forgotten, or simply never studied, leading us to overestimate how replicable the survivors' specific choices actually are.
Wald's bomber example makes the mechanism precise: reinforcing the bullet-hole locations visible on returning planes would have been actively wrong, because those planes survived their damage — the areas with no visible damage on survivors were the areas where a hit was fatal, information only visible by reasoning about the missing, non-surviving planes rather than the ones you can actually see and study.
What was Abraham Wald's key insight about WWII bomber planes and where to add armor?
Read more about the topic
The explanation above is written with AI assistance. These are the originals — go to them to check it.
- What Sharks (and Building Bombers) Teach Us About Survivorship BiasFarnam Street
- The Narrative FallacyFarnam Street
What Sharks Can Teach Us About Survivorship Bias
"Our fear of great white sharks — and our comparative indifference to more dangerous species like the oceanic whitetip — is itself a case of survivorship bias: we only hear stories from people who survived an attack and lived to describe it, which skews our sense of what's actually dangerous."