# Survivorship bias

*Also called: Selection on the outcome*

- **Cluster:** Evidence and sampling — The data that was gathered, and the data that was not
- **Page:** https://fallacy.wiki/fallacy/survivorship/
- **In Arabic:** https://fallacy.wiki/ar/fallacy/survivorship.md
- **Licence:** CC BY 4.0 — https://creativecommons.org/licenses/by/4.0/

## What it is

Studying only the cases that made it through, so the failures never enter the sample.

## In the wild

> Every successful founder dropped out, so dropping out helps.

## How to answer it

Ask where the failures went, and count them too.

## Origin and naming

The classic illustration is Abraham Wald at the Statistical Research Group during the Second World War: asked where to add armour on bombers, he studied the holes on planes that came back and armoured the spots that showed none — those were the planes that never returned. The term 'survivorship bias' now covers any sample that filtered out its own failures.

## More places it shows up

- A profile of unicorn founders notes they all worked eighty-hour weeks — with no column for the founders who did the same and folded.
- A music magazine asks arena headliners how they made it and takes 'just keep playing anywhere' as career advice.
- A property seminar interviews landlords who bought cheap in 2009 and generalizes their timing into a law of markets.
- A mutual fund's brochure touts its ten-year returns, calculated over the funds that survived the decade; the shuttered ones are off the books.

## How to spot it

- Advice comes only from people whose strategy visibly worked — losers were not invited to the panel.
- The dataset 'begins' at a point when failures were already filtered out; nobody quotes the full intake.
- Ask 'who tried this and failed?' and the room has no names to give.

## Nearby

- [Cherry picking](https://fallacy.wiki/fallacy/cherry-picking.md)
- [Anecdotal evidence](https://fallacy.wiki/fallacy/anecdotal.md)
- [Base rate neglect](https://fallacy.wiki/fallacy/base-rate.md)

## Read more

- [Wikipedia](https://en.wikipedia.org/wiki/Survivorship_bias)
- [Wikipedia: Abraham Wald](https://en.wikipedia.org/wiki/Abraham_Wald)

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From fallacy.wiki — a bilingual field guide to 91 logical fallacies, published by phi holdings. Licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/): reuse freely with attribution to fallacy.wiki.