Antifragility, Robustness, and Fragility, Inside the 'Black Swan' Domain
Nassim Nicholas Taleb
New York University-Poly School of Engineering
September 1, 2010
This discussion makes the distinction inside the Fourth Quadrant "Black Swan Domain" between fragile and robust to model (or representational) error on the basis of convexity. The notion of model error as a convex or concave stochastic variable; why deficit forecasting errors are biased in one direction; why large is fragile to errors; how economics as a discipline made the monstrously consequential mistake of treating estimated parameters as nonstochastic variables and why this leads to fat-tails even while using Gaussian models; the notion of epistemic uncertainty as embedded in model errors.
In addition, it introduces a simple practical heuristic to measure (as an indicator of fragility) the sensitivity of a portfolio (or balance sheet) to model error. Finally, it sets an explicit path to conduct policy based on robustness.
Date posted: August 31, 2010 ; Last revised: July 14, 2012
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