Denominator Neglect
Version 1.0.0 · Updated 2026-07-30
CORE DEFINITION
When evaluating risk, people often focus only on the numerator (how many bad events occurred) while ignoring the denominator (the total number of attempts). For example, seeing news reports of 5 vaccine side effects may lead one to think the vaccine is dangerous, forgetting that the denominator is hundreds of millions of vaccinations.
SCAFFOLDING EFFECT
Reduce cognitive load
Arithmetic against panic. When the media bombards you with vivid individual cases (numerators), force yourself to seek out the silent, huge denominator. Numbers without a denominator have no statistical significance.
Anchor fast decisions
Proposed by Barbara Spellman et al. ("denominator neglect"). People's intuitive judgments of risk are dominated by the availability heuristic—vivid cases (numerators) are easily accessible, while the abstract denominator of base rates is hard to think of, leading to overestimation of low-probability events. The mechanism is "availability > statistics".
MINIMUM ACTION
In progress 0/4Practice this model in one real situation:
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Source support: Explicit
- en.wikipedia.orghttps://en.wikipedia.org/wiki/Denominator_neglectverified
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