What is Excess Kurtosis and Why is it Important in Financial Analysis?

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    Gaussian Statistics
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Discussion Overview

The discussion revolves around the concept of excess kurtosis and its significance in financial analysis, particularly in relation to the assumptions of Gaussian statistics and the implications of non-Normal distributions in economic variables.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants express curiosity about the term "Gaussian statistics" and seek a layman's definition.
  • One participant explains that the Normal Distribution, also known as the Bell Curve or Gaussian distribution, is often assumed in economic models, but this assumption can lead to significant errors.
  • The collapse of Long-Term Capital Management is cited as an example where reliance on the Normal Distribution was problematic.
  • Another participant mentions that excess kurtosis indicates a distribution with heavier tails than a normal distribution, which is relevant in finance due to the potential for unforeseen risks.
  • Excess kurtosis and skewness are highlighted as critical factors that have gained attention in financial analysis, emphasizing the importance of testing normality assumptions.

Areas of Agreement / Disagreement

Participants generally agree on the significance of understanding excess kurtosis and the limitations of assuming normality in financial contexts. However, the discussion includes varying levels of detail and understanding regarding the implications of these concepts.

Contextual Notes

The discussion does not resolve the complexities surrounding the implications of excess kurtosis or the specific conditions under which Gaussian assumptions fail. There is also a lack of consensus on the best resources for further reading on the topic.

Who May Find This Useful

This discussion may be useful for individuals interested in financial analysis, statistical modeling, and the implications of distribution assumptions in economic contexts.

bballwaterboy
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I heard a guy mention in a debate that some math calculation didn't obey Gaussian statistics. It was a debate re: the economy (not important here, though).

I was curious what was meant by "Gaussian statistics" and would appreciate if anyone could offer a sort of layman's definition. Thanks so much!
 
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He was probably saying that some economic random variable did not have a Normal Distribution. The Normal Distribution is also known as the 'Bell Curve' as well as the 'Gaussian distribution' (because it was first invented by CF Gauss). Many random phenomena are assumed to be Normally Distributed because it makes calculations about them easier. But in some cases that assumption is very inaccurate, and that can cause big, unforeseen accidents.
The collapse of the hedge fund Long-Term Capital Management in 1998 is believed to have arisen from the fund managers assuming that certain economic variables were Normally Distributed when they were not.
 
andrewkirk said:
believed to have arisen from the fund managers assuming that certain economic variables were Normally Distributed when they were not.

I'd be interested in reading more about that, but I didn't see much about it in the wiki.
 
ElijahRockers said:
I'd be interested in reading more about that, but I didn't see much about it in the wiki.
This short article is more helpful, and points to a book by Benoit Mandelbrot all about the danger of the Gaussian assumption.

'Kurtosis' - the fourth moment of the distribution - measures how 'fat' the 'tails' of the distribution are. 'Excess kurtosis' is when there is more probability weight in the tails of a distribution than in a normal distribution with the same first two moments. Excess kurtosis - aka 'fat tails' - along with asymmetry (aka skew - related to the third moment) are problems that get a great deal of attention in finance these days, where it has belatedly been realized that testing the validity of assumptions of normality is very important.
 
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