A black swan is an extremely rare event with severe consequences. It cannot be predicted beforehand, though many claim it should be predictable after the fact. Black swan events can cause catastrophic damage to an economy, and because they cannot be predicted, can only be prepared for by building robust systems.
The term was popularised by Nassim Nicholas Taleb, a finance professor who argued that even though they are impossible to predict due to their extreme rarity, it is important for people to assume that a black swan event is a possibility and plan accordingly.
Example- The financial crash of the U.S. housing market during the 2008 crisis is one of the well-known black swan events. The effect of the crash was catastrophic and global, and only a few outliers were able to predict it happening.
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