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Base Rates

Your specific plan feels like evidence. It's usually just the same story everyone in the base rate also told themselves.

Decision MakingSeason 1probabilityforecasting

2 min read

INSIDE VIEW × OUTSIDE VIEW
YOUR ESTIMATE18 months
BASE RATE (SIMILAR PROJECTS)34 months
YOUR STORY FEELS DIFFERENTIT USUALLY ISN'T

Core question: how do you judge the odds of something you've never personally experienced before?

The metaphor: the inside view and the outside view

Every renovation believes it'll finish on schedule. Every founder believes their startup is the exception. That confidence comes from the inside view — the specific plan, the specific reasons, the specific people involved. The base rate is the outside view instead: what happened, on average, to everyone else who was in a roughly similar position, regardless of what their plan or reasoning looked like at the time. Most people trust the inside view completely and barely glance at the base rate — which is exactly backwards, since the people in that base rate had their own confident, specific reasons too.

The base rate matters more, not less, the more confident your inside-view story feels. Every plan that later failed felt just as solid to the person holding it as your plan feels to you right now.

Finding the base rate is a specific, separate step

Before estimating from your own plan, ask a different question first: what fraction of roughly similar attempts succeeded, historically? Construction projects overrun their timeline by a predictable amount, on average. Startups in a given category survive a predictable number of years, on average. Use that number as the starting point, then adjust it only for genuine, verifiable differences about your specific situation — not for the fact that your reasons feel compelling to you, since everyone's do.

Before trusting your own estimate, ask: if I described this exact situation to someone with no attachment to my plan, what would they guess the base rate is? Answer that before defending why you're the exception.

Why this matters

The inside view is where motivation and planning happen — it's genuinely useful for deciding what to do. It's a bad tool for estimating the odds of success, because it was never built to be honest about the odds. The base rate is colder, less flattering, and far more often right.