Fat Tail Events

Fat Tail Events denote uncommon, large deviations from averages, often linked with significant financial shifts. These are characterized by a greater likelihood of extreme occurrences than typical predictions suggest. Their profound impact, as witnessed in events like the 2008 financial crisis, underscores the importance of understanding and managing such phenomena.

Fat Tail Events Definition

These are extreme events that occur in the tail ends of a probability distribution. They are named for the shape of the distribution curve, which is fatter or wider in the tails than a normal distribution curve.

Importance in Financial Markets

Fat tail events are of significant concern in financial markets because they represent substantial, unexpected shifts, often causing substantial gains or losses.

Role of Standard Deviation

Standard deviation is often used in statistics to measure the spread of data. However, in fat-tail distributions, standard deviation becomes less useful because it underestimates the probability of extreme events.

Types of Fat Tails

There are two types of fat tails – positive and negative. Positive fat tails represent larger than expected gains, while negative fat tails represent larger than expected losses.

Heavy-tailed Distribution

A heavy-tailed distribution is another term often used to describe fat-tail distributions. It is a probability distribution whose tails are not exponentially bounded.

Normal Distribution vs Fat Tails

In a normal distribution, extreme events are considered highly unlikely. However, in a fat-tail distribution, the likelihood of extreme events is higher.


This is a statistical measure that describes the tails and sharpness of a distribution. Higher kurtosis indicates a higher likelihood of fat-tail events.

Impact of Fat Tail Events

These events often have significant effects on economies and financial markets. Examples include the 2008 financial crisis and the dotcom bubble burst.

Black Swan Events

This term, coined by Nassim Nicholas Taleb, is often associated with fat tail events. Black Swan events are unpredictable events that have massive impacts and are rationalized with the benefit of hindsight.

Pareto Principle

Often associated with fat-tail events, this principle states that roughly 80% of effects come from 20% of causes. In fat-tail distributions, a small number of events can have a large impact.

Mitigation Strategies

Some strategies used to manage the risk of fat tail events include diversification, hedging, and the use of fat-tail risk metrics.

Fat Tails in Other Fields

Fat tail events aren’t just pertinent to financial markets. They also apply in areas like meteorology, where certain extreme weather events follow a fat-tail distribution.