The Black Swan theory

le lundi, c'est épistémologie...

En fouillant le net à la recherche d'un article sur la sécurité informatique je suis tombé sur cette jolie théorie du cygne noir. Une analyse de Mr Nassim Taleb qui renvoie dans leurs 22m les gentils analystes du Marché omnipotent (entre autre et pas mal de chercheurs en science humaines je pense).

En voici quelques extraits savoureux:

Globalization creates interlocking fragility, while reducing volatility and giving the appearance of stability. In other words it creates devastating Black Swans. We have never lived before under the threat of a global collapse. Financial Institutions have been merging into a smaller number of very large banks. Almost all banks are interrelated. So the financial ecology is swelling into gigantic, incestuous, bureaucratic banks – when one fails, they all fall. The increased concentration among banks seems to have the effect of making financial crises less likely, but when they happen they are more global in scale and hit us very hard. We have moved from a diversified ecology of small banks, with varied lending policies, to a more homogeneous framework of firms that all resemble one another. True, we now have fewer failures, but when they occur ….I shiver at the thought.

Banks hire dull people and train them to be even more dull. If they look conservative, it's only because their loans go bust on rare, very rare occasions. But (...)bankers are not conservative at all. They are just phenomenally skilled at self-deception by burying the possibility of a large, devastating loss under the rug.

The government-sponsored institution Fannie Mae, when I look at its risks, seems to be sitting on a barrel of dynamite, vulnerable to the slightest hiccup. But not to worry: their large staff of scientists deemed these events "unlikely".

There is no way to gauge the effectiveness of their lending activity by observing it over a day, a week, a month, or . . . even a century!

(...) the real- estate collapse of the early 1990s in which the now defunct savings and loan industry required a taxpayer-funded bailout of more than half a trillion dollars. The Federal Reserve bank protected them at our expense: when "conservative" bankers make profits, they get the benefits; when they are hurt, we pay the costs.

Once again, recall the story of banks hiding explosive risks in their portfolios. It is not a good idea to trust corporations with matters such as rare events because the performance of these executives is not observable on a short-term basis, and they will game the system by showing good performance so they can get their yearly bonus. The Achilles’ heel of capitalism is that if you make corporations compete, it is sometimes the one that is most exposed to the negative Black Swan that will appear to be the most fit for survival.

As if we did not have enough problems, banks are now more vulnerable to the Black Swan and the ludic fallacy than ever before with “scientists” among their staff taking care of exposures. The giant firm J. P. Morgan put the entire world at risk by introducing in the nineties RiskMetrics, a phony method aiming at managing people’s risks, causing the generalized use of the ludic fallacy, and bringing Dr. Johns into power in place of the skeptical Fat Tonys. (A related method called “Value-at-Risk,” which relies on the quantitative measurement of risk, has been spreading.)

Please, don’t drive a school bus blindfolded.

Owing to [...] misunderstanding of the causal chains between policy and actions, we can easily trigger Black Swans thanks to aggressive ignorance—like a child playing with a chemistry kit.

Si la théorie du chaos vous fascine et que la magie statisticienne "vu à la télé" vous à toujours un peu étonné, voici quelques articles résumant la sympathique théorie du cygne noir, pendant naturel du gentil chaos.

Le NY times


Analyse universitaire

Mon prochain livre de chevet, je pense...

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