By Marco BösingWhat Is a Black Swan Event?
A Black Swan event is an occurrence defined by three core characteristics: it is extremely improbable, has massive impact on markets and society, and is rationalized after the fact as if it were predictable. The concept was coined by risk analyst and author Nassim Nicholas Taleb in his 2007 book of the same name.
Historical examples of Black Swan events in financial markets include the collapse of Lehman Brothers in 2008, the Flash Crash of May 2010, the Swiss National Bank's abandonment of the franc's peg in January 2015, and the COVID-19 crash in March 2020.
For traders, Black Swan events serve as a reminder to never underestimate tail risk. Although such events occur rarely, they can wipe out accounts within minutes. Robust risk management — including position size limits, stop-loss orders, and diversification — remains the only reliable defense.