Improbability Factor
The dangerous assumption that because a known error is unlikely, it won't happen. In complex systems, improbable events become inevitable given enough time or scale.
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Origin
The idea has no single coinage but crystallized through key works on systemic risk. In 1984, sociologist Charles Perrow argued in Normal Accidents that the complexity and tight coupling of modern systems makes "unlikely" failures essentially inevitable over time. Nassim Nicholas Taleb extended this in his 2007 book The Black Swan, arguing that rare, high-impact events are systematically underestimated because models anchor to past experience rather than tail-risk probability.
Updated February 22, 2026