Finiteness of variance and its limitations in quantitative finance

For our 4/26 discussion, a paper by Nassim Taleb, with his typical choleric flair:

“Outside the Platonic world of financial models, assuming the underlying distribution is a scalable “power law”, we are unable to find a consequential difference between finite and infinite variance models –a central distinction emphasized in the econophysics literature and the financial economics tradition. While distributions with power law tail exponents α>2 are held to be amenable to Gaussian tools, owing to their “finite variance”, we fail to understand the difference in the application with other power laws (1<α<2) held to belong to the Pareto-Lévy-Mandelbrot stable regime. The problem invalidates derivatives theory (dynamic hedging arguments) and portfolio construction based on mean-variance. This paper discusses methods to deal with the implications of the point in a real world setting.”

Link to paper

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