Back in 2011 I led a Science Circle discussion on Black Swans (See link below for transcript). I am still fascinated by these phenomena and want to revisit them now after almost 9 years.
A brief recap: A black swan is a highly improbable event with three principal characteristics: It is unpredictable; it carries a massive impact; and, after the fact, we seek explanations so we might prevent or predict future events (Taleb, 2010). A black Swan may have a positive or a negative effect. The astonishing success of Google was a black swan; so were the terror attacks of 9/11. Specifically however, we see Black Swans as always disruptive and usually negative.
Generally, the literature has focused on the occurrence of Black Swan events in finance and business. Politics and war also have their Black Swans. As do the geological and biological sciences.
I did find several articles in the science area. Anderson et al (2017) looked at Black Swan events in animal populations. They identify many events of rapid species collapse that are Black Swans. Nuñez & Logares (2012) looked at Black Swans in ecology and evolution.
Now not every catastrophe is a Black Swan. There are criteria: Veisdal (2019) says, “For an event to be classified as a black swan event, it must be ex ante computationally inaccessible.” In other words it must be unpredictable.
Hurricanes are, for the most part, predictable and so generally are not Black Swans. At one time a meteor strike on the earth would have been unpredictable but now we have a pretty good handle on the objects in our solar system that may come our way.
“… a black swan is by definition a surprise. Nevertheless, people tend to concoct explanations for them after the fact, which makes them appear more predictable, and less random, than they are. Our minds are designed to retain, for efficient storage, past information that fits into a compressed narrative. This distortion, called the hindsight bias, prevents us from adequately learning from the past” (Taleb, 2004).
Black Swans are associated with probabilities. We are all familiar with the normal distribution. It is that bell shaped curve that shows the distribution of many common variables in any population. For example, the height of humans varies and about 70% of all people’s heights fall within one standard deviation of the mean height of all people. Roughly, 95% fall within two standard deviations and 99% within three. Black Swans are rarer still. They are so unlikely that we would expect them never to happen. The strange thing is they happen more often than probabilities would indicate.
That is what so fascinates me about black Swans. They are those events we never expect, cannot plan for but really think we should do something to prevent. It is this psychological tension that is so frustrating and so human.
- Anderson, SC, Branch, TA, Cooper, AB, and Dulvy, NK. Black-swan events in animal populations, Proceedings of the National Academy of Sciences, March 21, 2017.
- Buchanan, M. In Search of the Black Swans, Physics World, Apr 1, 2009.
- Cressie, N. Uncertainty, Statistical Science, and Black Swans, Statistics Views, Jul 5, 2017.
- Faisal, K. 9 Black Swan Events that changed the Financial World, Data Driven Investor, Jan 18, 2019.
- La Roche, J. Taleb: People should not try to predict ‘black swan’ events, Yahoo Finance, May 18, 2019.
- Nuñez MA, & Logares R. Black Swans in ecology and evolution: The importance of improbable but highly influential events, Ideas Ecol Evol, 2012, 5, 16–21.
- Oh, D. The Black Swan: Probability and Human Decision Making, Science Circle, Apr 5, 2011.
- Phys.org. ‘Black swan’ events strike animal populations, Phys.org, Mar 7, 2017.
- Taleb NN. The Black Swan: The Impact of the Highly Improbable. Random House Inc., New York, 2007.
- Taleb, NN. The Fourth Quadrant: A map of the Limits of Statistics, Edge, Sep 14, 2008.
- Veisdal, J. What is a Black Swan event? – Necessary and sufficient conditions, Cantor’s Paradise, Sep 6, 2019
- Wade, K. Three themes for 2019 – and some black swans, Schroders, Jan 23, 2019.