Black Swan Event A black swan event  is a term coined by Nassim Nicholas Taleb in his 2007 book The Black Swan . It refers to an unpredictable, high-impact occurrence that: Lies outside normal expectations (extremely rare and unforeseeable based on prior data or models). Has massive consequences (e.g., economic, social, or geopolitical upheaval). Is rationalized in hindsight with explanations that make it seem predictable. Examples : The 9/11 attacks (2001): Unanticipated sca