Taleb on the failures of financial economics

Nassim Nicholas Taleb writes in Financial Times that because financial economics focus on normal and marginal behaviour at the expense of shocks and market reorganizations it is a pseudo-science hurting markets:

I was a trader and risk manager for almost 20 years (before experiencing battle fatigue). There is no way my and my colleagues’ accumulated knowledge of market risks can be passed on to the next generation. Business schools block the transmission of our practical know-how and empirical tricks and the knowledge dies with us. We learn from crisis to crisis that MPT [modern portfolio theory] has the empirical and scientific validity of astrology (without the aesthetics), yet the lessons are ignored in what is taught to 150,000 business school students worldwide.

Academic economists are no more self-serving than other professions. You should blame those in the real world who give them the means to be taken seriously: those awarding that “Nobel” prize.

In 1990 William Sharpe and Harry Markowitz won the prize three years after the stock market crash of 1987, an event that, if anything, completely demolished the laureates’ ideas on portfolio construction. Further, the crash of 1987 was no exception: the great mathematical scientist Benoît Mandelbrot showed in the 1960s that these wild variations play a cumulative role in markets – they are “unexpected” only by the fools of economic theories.

Then, in 1997, the Royal Swedish Academy of Sciences awarded the prize to Robert Merton and Myron Scholes for their option pricing formula. I (and many traders) find the prize offensive: many, such as the mathematician and trader Ed Thorp, used a more realistic approach to the formula years before. What Mr Merton and Mr Scholes did was to make it compatible with financial economic theory, by “re-deriving” it assuming “dynamic hedging”, a method of continuous adjustment of portfolios by buying and selling securities in response to price variations.

Dynamic hedging assumes no jumps – it fails miserably in all markets and did so catastrophically in 1987 (failures textbooks do not like to mention).

Later, Robert Engle received the prize for “Arch”, a complicated method of prediction of volatility that does not predict better than simple rules – it was “successful” academically, even though it underperformed simple volatility forecasts that my colleagues and I used to make a living.

The environment in financial economics is reminiscent of medieval medicine, which refused to incorporate the observations and experiences of the plebeian barbers and surgeons. Medicine used to kill more patients than it saved – just as financial economics endangers the system by creating, not reducing, risk. But how did financial economics take on the appearance of a science? Not by experiments (perhaps the only true scientist who got the prize was Daniel Kahneman, who happens to be a psychologist, not an econ­omist). It did so by drowning us in mathematics with abstract “theorems”. Prof Merton’s book Continuous Time Finance contains 339 mentions of the word “theorem” (or equivalent). An average physics book of the same length has 25 such mentions. Yet while economic models, it has been shown, work hardly better than random guesses or the intuition of cab drivers, physics can predict a wide range of phe­nomena with a tenth decimal precision.

via 3quarks daily.

For more see Taleb’s home page – Fooled by Randomness.

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