Sunday, June 6, 2010

John Hussman Commentary

I find John Hussman's weekly commentaries on financial markets very informative, mostly because they are very different from noise that important looking "experts" with (faulty?) crystal balls spew on CNBC. Sometime back, I linked to this page, which clearly demonstrates that forecasters, as a group, merely extrapolate the past into the future.

This is a great disservice, because most of the numbers that these experts divine, pretty useless from a practical standpoint. In addition, the mask of conviction with which these experts conduct themselves instills a false sense of confidence in people who like to listen to such talking heads.

I like John Hussman's balanced commentaries because of the how heavily he uses concepts of probability, and Bayesian inference in his analysis. I wish they taught this stuff more widely. For example, in his most recent commentary linked above, he comments about the Gulf of Mexico oil-spill:
With regard to oil spills, however low one might have believed P(we'll have an oil spill) to be, prior to the recent accident, the "prior" probability estimate should change given that we've now observed one of the worst oil spills in history. Even if the oil industry previously argued that the probability of an oil spill was one in a million, it's hard to hold onto that assessment after the oil spill occurs, unless your faith in the soundness of the technology is entirely unmoved in the face of new information.
(John Maynard Keynes would have paraphrased it as: "When the facts change, I change my mind. What do you do sir?")

Hussman goes on to do a back-of-the-envelope calculation which suggests that since the number of deep sea oil rigs has increased dramatically, the chances of seeing catastrophic oil spills are actually quite significant.

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