Closely related: the planning fallacy is the bias itself — you underestimate how long things take — and Hofstadter's law is the wry admission that even knowing about the bias doesn't fully fix it.
| The planning fallacy | Hofstadter's law | |
|---|---|---|
| What it is | Underestimating time or cost despite past evidence | The joke that even correcting for the fallacy still runs late |
| Origin | A documented cognitive bias | A recursive aphorism (Douglas Hofstadter) |
| The lesson | Use outside-view estimates from similar past projects | Pad your padded estimate — and expect to still be surprised |
The planning fallacy explains why your estimate is too optimistic. Hofstadter's law is the punchline: even after adjusting for the planning fallacy, the adjusted estimate still runs long. Treat it as permission to build in real slack, not just a bigger number.
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