A black swan is an extremely rare event with dire consequences.
It is impossible to predict in advance, although after the fact many people mistakenly claim that it should have been predictable.
Black swan events can cause catastrophic damage to the economy, negatively affecting markets and investment, but even the use of reliable modeling cannot prevent a black swan event.
Relying on standard forecasting tools can not only fail to predict, but potentially increase vulnerability to black swans, spreading risk and offering false security.
– The term was popularized thanks to Nassim Nicholas Taleb’s book The Black Swan.