Grey Swan

What Is a Grey Swan?

Grey swan is a term used to describe a potentially very significant event whose possible occurrence may be predicted beforehand but whose probability is considered small. In other words, it is a risk with a potentially large impact but a low perceived likelihood of happening. Because there is a slight chance the event will occur it should be anticipated, particularly as it could shake up the world economy and stock market.

Key Takeaways

  • A grey swan is an event that is possible and known, potentially extremely significant but considered not very likely to happen.
  • The term grey swan is a play on Taleb's concept of an unpredictable black swan event, but is fundamentally different in that it is predictable.
  • Grey swans can be positive or negative and significantly alter the way the world operates, which is why we are urged to take them seriously.
  • Examples of grey swans include climate change, population growth, and rising debt.

Understanding Grey Swan

Grey swans are not viewed as entirely improbable, meaning the possibility of their occurrence is known beforehand. They can be positive or negative and significantly alter the way the world operates, which is why we are urged to take them seriously.

Examples include natural disasters, such as Katrina, Britain’s unexpected decision to leave the European Union (EU), otherwise known as Brexit, Donald Trump winning the 2016 U.S. presidential election, or a revolutionary technological breakthrough, such as the internet.

The outcome of these types of events cannot necessarily be predicted with ease. However, that does not mean that those who stand to be affected should not draw up some form of a plan for how to potentially handle them, regardless of how improbable they might seem.

Grey Swan vs. Black Swan vs. White Swan

Grey swan is a by-product of black swan, a term popularized by finance professor, writer, and former Wall Street trader Nassim Nicholas Taleb. In his book, The Black Swan: The Impact of the Highly Improbable, Taleb described a black swan as an entirely unpredictable event that is beyond what is normally expected of a situation and has potentially severe consequences. 

He outlined the three core attributes of a black swan as:

1) An outlier because nothing in the past can convincingly point to its possibility.

2) Carrying an extreme impact.

3) Something that can be rationally explained after it occurs.

Taleb’s theory went on to become a fashionable way to classify all catastrophes. Then some observers began to note that not all big things that happen are out of the blue and completely improbable. Instead, some events are clearer and slightly easier to see coming, and not just in hindsight.

From there, the terms grey and white swan were born. The former is used to describe events that are more predictable than black swan ones, while the latter is characterized as something almost certain to happen.

Taleb's book does not define the term grey swan and would classify such events as just commonplace risks.

Black, grey, and white swans also vary in terms of the impact they are perceived to have. White swans are said to have little implications, impacting the life of one or a group of people rather than the entire globe. Grey swans, and even more so black swans, are viewed differently, causing events that can be potentially devastating for many. The main difference between the two is that one is known about beforehand, while the other takes us completely by surprise.

The risk management implications of gray swans are different, too. Gray swans can be managed by building what Taleb refers to as resilience, or robust capabilities. Financial buffers, surplus production and supply chain capacity, built-in redundancies, and real options can help to withstand the impact of gray swans. Dealing with black swans goes beyond just building resilience, but becoming antifragile.

Examples of Grey Swans

Everything from climate change, population growth, and rising debt have been categorized as grey swans. We are aware of their presence, but perhaps do not take them seriously enough, even if each of them could end up having severe, wide-ranging consequences, such as triggering an earthquake or another Great Depression.

The Covid-19 pandemic is an example of a gray swan. Pandemics are a rare but well-acknowledged risk that the world has experienced repeatedly in the past, from the Justinian Plague to the Black Death and the Spanish Flu. Though the risk of a pandemic in any given year is estimated to be quite low based on past frequency, they can have dramatic and transformative effects on the economy and society.

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  1. Nassim Nicholas Taleb. "The Black Swan: The Impact of the Highly Improbable." Random House; 2007.