這些事肯定都會在 2017 年發生。但真正的黑天鵝事件是什麼？——亦即現在不在我們的視野之內，卻會擾亂金融市場的事件？
From Wikipedia, the free encyclopedia
The black swan theory or theory of black swan events is a metaphor that describes an event that comes as a surprise, has a major effect, and is often inappropriately rationalized after the fact with the benefit of hindsight. The term is based on an ancient saying which presumed black swans did not exist, but the saying was rewritten after black swans were discovered in the wild.
The theory was developed by Nassim Nicholas Taleb to explain:
- The disproportionate role of high-profile, hard-to-predict, and rare events that are beyond the realm of normal expectations in history, science, finance, and technology.
- The non-computability of the probability of the consequential rare events using scientific methods (owing to the very nature of small probabilities).
- The psychological biases which blind people, both individually and collectively, to uncertainty and to a rare event's massive role in historical affairs.
Unlike the earlier and broader "black swan problem" in philosophy (i.e. the problem of induction), Taleb's "black swan theory" refers only to unexpected events of large magnitude and consequence and their dominant role in history. Such events, considered extreme outliers, collectively play vastly larger roles than regular occurrences.:xxi More technically, in the scientific monograph 'Silent Risk', Taleb mathematically defines the black swan problem as "stemming from the use of degenerate metaprobability".
The phrase "black swan" derives from a Latin expression; its oldest known occurrence is the poet Juvenal's characterization of something being "rara avis in terris nigroque simillima cygno" ("a rare bird in the lands and very much like a black swan").:165 When the phrase was coined, the black swan was presumed not to exist. The importance of the metaphor lies in its analogy to the fragility of any system of thought. A set of conclusions is potentially undone once any of its fundamental postulates is disproved. In this case, the observation of a single black swan would be the undoing of the logic of any system of thought, as well as any reasoning that followed from that underlying logic.
Juvenal's phrase was a common expression in 16th century London as a statement of impossibility. The London expression derives from the Old World presumption that all swans must be white because all historical records of swans reported that they had white feathers. In that context, a black swan was impossible or at least nonexistent.