Extreme Risk
Tail Risk · Black Swan Events
Risks of very bad outcomes or "high consequence", but of low probability. They include the risks of terrorist attack, biosecurity risks such as the invasion of pests, and extreme natural disasters such as major earthquakes.
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Origin
Nassim Nicholas Taleb articulated black swan theory starting in 2001, formalized in his 2007 book The Black Swan. Taleb described rare, high-impact events lying in the "fat tails" of probability distributions—events like World War I, the Internet's rise, and 9/11. His framework challenged conventional risk management, arguing that rather than trying to predict black swans, organizations should reduce overall vulnerability to extreme events.
Updated February 22, 2026