Tuesday, March 10, 2009

Why I never got a job on Wall Street:

From a so-so primer about "quants" in today's NY Times:

One of the most outspoken critics is Nassim Nicholas Taleb, a former trader and now a professor at New York University. He got a rock-star reception at the World Economic Forum in Davos this winter. In his best-selling book “The Black Swan” (Random House, 2007), Dr. Taleb, who made a fortune trading currency on Black Monday, argues that finance and history are dominated by rare and unpredictable events.

“Every trader will tell you that every risk manager is a fraud,” he said, and options traders used to get along fine before Black-Scholes. “We neverhad any respect for nerds.”

Dr. Taleb has waged war against one element of modern economics in particular: the assumption that price fluctuations follow the familiar bell curve that describes, say, IQ scores or heights in a population, with a mean change and increasingly rare chances of larger or smaller ones, according to so-called Gaussian statistics named for the German mathematician Friedrich Gauss.

But many systems in nature, and finance, appear to be better described by the fractal statistics popularized by Benoit Mandelbrot of IBM, which look the same at every scale. An example is the 80-20 rule that 20 percent of the people do 80 percent of the work, or have 80 percent of the money. Within the blessed 20 percent the same rule applies, and so on. As a result the odds of game-changing outliers like Bill Gates’s fortune or a Black Monday are actually much greater than the quant models predict, rendering quants useless or even dangerous, Dr. Taleb said.

I suspect if you go over the books of these places, you'll find that very little pure R&D was done.

Dr. Taleb is right (to a point) though I would have used (and still do, in fact in other contexts) different models.

My thesis was in the area of nonlinear detection and estimation in dependent non-Gaussian noise.

I guess I was over-educated for Wall Street.

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