Recent Blog Posts
-
The Times' Rorshach Geithner Story
Apr 27 20099:04am EDT -
Sinking Animal Spirits
Apr 27 20098:04am EDT -
Counter-cyclical Urban Policy
Apr 26 200910:04am EDT -
Be Your Own Counterfeiter
Apr 26 20099:04am EDT -
Being Tim Geithner
Apr 25 200912:04pm EDT -
Notes From a Press Conference Naif
Apr 25 20099:04am EDT -
What Good is the News?
Apr 25 20098:04am EDT -
Stressful Enough
Apr 24 20092:04pm EDT -
Not Regretting the Pound
Apr 24 20091:04pm EDT -
Introducing the New Ford Squeeze
Apr 24 20099:04am EDT -
Non-Economic Questions of the Day
Apr 24 20099:04am EDT -
The Stress Test Blind Alley
Apr 24 20098:04am EDT -
Happy Hour
Apr 23 20099:04pm EDT -
Recovery Without Rebalancing
Apr 23 20096:04pm EDT -
The Shape of Your Recession
Apr 23 20095:04pm EDT
Links
- Felix Salmon

- DealBreaker

- Ryan Avent: The Bellows

- The Epicurean Dealmaker

- Chris Anderson

- Ultimi Barbarorum

- MarketBeat

- Michelle Leder

- John Quiggin

- The Panelist

- Andrew Leonard

- Streetsblog

- Brad Setser

- Michael Mandel

- Financial Crookery

- Kash Mansori

- Dean Baker

- Calculated Risk

- Free Exchange

- Curbed

- Lance Knobel

- Econospeak

- Carbon Tax Center

- Overcoming Bias

- Mark Thoma

- Naked Capitalism

- Alphaville

- Barry Ritholtz

- Alexander Campbell

- The Bayesian Heresy

- Brad DeLong

- DealBook

- Greg Mankiw

- Deal Journal

- FP Passport

- Carl Bialik

- Marginal Revolution

- A Fistful of Euros

- Dan Gross

Has Nassim Taleb Killed Black-Scholes?
Nassim Taleb and Espen Haug have a paper out. Here's the abstract:
Options traders use a pricing formula which they adapt by fudging and changing the tails and skewness by varying one parameter, the standard deviation of a Gaussian. Such formula is popularly called Black-Scholes-Merton owing to an attributed eponymous discovery (though changing the standard deviation parameter is in contradiction with it). However we have historical evidence that 1) Black, Scholes and Merton did not invent any formula, just found an argument to make a well known (and used) formula compatible with the economics establishment, by removing the “risk” parameter through dynamic hedging, 2) Option traders use (and evidently have used since 1902) the previous versions of the formula of Louis Bachelier and Edward O. Thorp (that allow a broad choice of probability distributions) and removed the risk parameter by using put-call parity. The Bachelier-Thorp approach is more robust (among other things) to the high impact rare event. It is time to stop calling the formula by the wrong name.
Over at BreakingViews (subscription required), Pablo Triana explains what this means:
The Black-Scholes-Merton (BSM) option pricing model won two of its authors a Nobel Prize in economics. But a potentially revolutionary paper by Nassim Taleb and Espen Haug has thrown the whole edifice into question...
BSM may be reduced to what Taleb and Haug deem a “marketing exercise”. All that BSM did is re-derive an already existing formula by using new and quite fragile theoretical arguments.
Even more dramatic and watersheddy, Taleb and Haug argue that actual option prices on the open market may be simply the result of the interaction of supply and demand, with no formula involved. That goes against BSM, which says demand forces should play no role in pricing...
Why is all this relevant? There are at least two crucial consequences. First, the whole role of quantitative finance is thrown into question...
The second implication of Taleb and Haug is that implied volatility, a ubiquitous element of the markets, ceases to make sense. In fact, it would cease to exist... Rather than being the “market´s expected future turbulence” or the “market´s fear gauge”, as conventional wisdom would hold, implied volatility would have proven itself to be nothing but make-believe. A nonexistent ghost.
Now I'm not remotely educated enough in such matters to critically assess the Haug-Taleb paper, or its interpretation by Triana. But I am looking forward to a spirited debate.
(Via Kedrosky)






