What Is Tail Risk?
There are moments when, after being quiet for a while, a -30% or -80% arrives once every few years. We look at why this risk hidden in the 'tail' of the probability distribution is so frightening.
Where does the 'tail' refer to?
If you draw returns as a histogram, the middle (near the average) bulges and both ends stretch out thin. These thinly stretched ends are called the 'tails.'
Tail risk is the risk of extreme events occurring at these ends, especially the left tail (the large-loss side). The characteristic is that the probability is low, but once it happens, the scale of loss is overwhelming.
What's important is that the tails of the actual market are far fatter than a normal distribution predicts. An event at the level of 'once in ten thousand years in theory' actually happens several times over decades.
The tail events history has shown
Tail risk is not an abstract story. It has actually become reality several times.
- Black Monday 1987: The Dow plunged -22.6% in a single day (the worst single-day drop in history). The S&P 500 also fell about -20% in one day. - The 2008 financial crisis: The S&P 500 fell about -57% from its peak and took about 4–5 years to recover. - Bitcoin: Since 2014 there have been several drawdowns exceeding -50%, and the big ones reached about -80% on average. It once collapsed from a peak of about $69,000 in November 2021 to about $15,000 in November 2022.
What these events have in common is that 'no one saw them coming.' That's why tail risk especially wounds those who watched only 'normal-times volatility.'
Historical figures vary slightly by source (e.g., the 2008 S&P drop of -55 to -57%, bitcoin drawdown of -78 to -84%). Here they are written as rough ranges. Exact figures vary depending on the period and measurement method.
How to deal with tail risk
Tail risk is not something 'you can eliminate.' As long as you participate in the market, you will meet it someday. So the key is not prediction but 'designing so you can endure it.'
- Know the drawdown in advance: If you accept that 'my assets could someday experience -50%,' you'll be less likely to panic-sell in that moment. - A bearable weight: Hold fat-tailed assets (crypto assets, individual stocks, etc.) only in an amount that won't shake your life even if they collapse. - Diversification: Mixing assets that move differently can reduce the shock of one asset's tail event (though during a crisis, correlations tend to rise together, so the effect can shrink).
On this site's crisis-case page, checking past crashes and recovery periods yourself helps you feel tail risk through the numbers.
Preguntas frecuentes
Q. Are tail risk and black swan the same thing?
Similar, but slightly different. Tail risk is a statistical concept referring to the whole 'risk of extreme losses occurring at the ends of the distribution.' A black swan is an expression emphasizing a specific event among those that was 'practically impossible to predict and had an enormous impact.' You could see a black swan as an extreme kind of tail risk.
Q. Does diversifying make tail risk disappear?
You can reduce it, but not eliminate it. Diversification does a good job of blocking accidents unique to individual assets, but in a crisis where the whole market collapses at once (a systematic event), correlations between assets spike together and the defensive power weakens. That's why, along with diversification, you need to set 'a weight you can endure.'
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📋 Los resultados se basan en datos históricos; las rentabilidades pasadas no garantizan rentabilidades futuras.
📋 Este servicio se ofrece con fines educativos para ayudarte a entender la inversión, no como asesoramiento de inversión.