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Base rate

The background probability before case-specific details are added.

Published 15 May 2026Updated 30 May 2026

A base rate is the general frequency of an event in the relevant population. It keeps judgment anchored before vivid details, anecdotes, or special-case explanations take over.

Sources

Judgment under Uncertainty: Heuristics and Biases

Science / 1974 / Paper

Classic heuristics and biases paper.