"Black Swan" is a term popularized by Nassim Nicholas Taleb's 2007 book, "The Black Swan: the Impact of the Highly Improbable." The book focuses on a common error people make in economic forecasting: they place too much weight on the odds that past events will repeat; however, really important economic and political events are rare and unpredictable.
"Black Swan" is a reference to a 17th century philosophical thought experiment. Europeans used the phrase "all swans are white" as the standard example of a scientific truth (because no one had seen any swans that were not white). The chance of seeing a black swan was thought to be impossible to calculate...until 1697, when they were found in Australia.
Thus the term Black Swan is used to mean a rare, high impact, and hard-to-predict event. Some examples Taleb uses are: the rise of Hitler, the demise of the Soviet bloc, the rise of Islamic fundamentalism, the spread of the Internet and the market crash of 1987. These events are predictable only in retrospect; human nature makes us concoct explanations for an occurrence after the fact, making it explainable and predictable.
Taleb first made this argument in "Fooled by Randomness," his book about the predilection for self-deception when it comes to statistics.
- The Black Swan: the Impact of the Highly Improbable. Amazon.com.
- The Black Swan, Chapter 1. The New York Times.