Risk
Black swan
A rare, high-impact event that was not predicted and is explained confidently afterwards.
How it works
The term describes three properties together: the event was an outlier relative to prior expectations, its impact was extreme, and human nature produced a tidy explanation for it after the fact.
The useful lesson is not to try to forecast them. It is to build portfolios that survive them — which means limiting leverage and avoiding structures that force selling at the worst moment.
Where it misleads people
The phrase gets applied to anything unpleasant. A predictable risk that people chose to ignore is not a black swan; it is a risk that people chose to ignore.
Related terms
- Fat tailsThe tendency of extreme market moves to happen far more often than standard statistics predict.
- Tail-risk hedgingDeliberately paying a small ongoing cost to limit losses in a severe market fall.
- Margin callA demand from your broker to add cash or sell holdings, because your account equity has fallen too low.
- LiquidityHow quickly you can turn something into cash at a fair price, without moving the price against yourself.
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Educational reference only. Nothing here is investment advice or a recommendation to buy or sell anything, and tax treatment depends on your own circumstances and the country you are in.