Friday, 24 June 2016

Fooled by randomness

I just finished reading the Nassim Nicholas Taleb book, Fooled by Randomness. It's more than ten years old (I read the second edition), but the insights are mostly timeless. I really enjoyed the first half of the book, but the second half was a bit less entertaining (for me at least). Perhaps I was just smarting by then from the constant quips against economists, such as "the general credibility of conventional economists has always been so low that almost nobody in science or in the real world ever pays attention to them", and "...economists, who usually find completely abstruse ways to escape reality...". Ok, perhaps we resemble that latter remark, so I should let him off. He rips journalists too, as "the greatest plague we face today", and MBAs, as "devoid of the smallest bit of practical intelligence".

At the time he wrote the book, Taleb had many years of Wall Street experience. The book essentially focuses on the role of randomness, with the central thesis that much of the 'success' that we observe (not just on Wall Street but in other diverse areas as well) simply results from randomness. This is best illustrated by an example (which I paraphrase from the book):

Take 10,000 fictional investment managers. Assume that they each have a perfectly fair game, where each one has a 50% probability of making $10,000 at the end of the year, and a 50% probability of losing $10,000. Further assume that once a manager has a single bad year, they are sacked. Now, after one year, we expect 5,000 managers to be up $10,000 each, and 5,000 to be down $10,000 (and out of a job). After two years, the number of managers remaining is 2,500, and 1,250 after three years. By the end of the fifth year, 313 managers remain, all of whom have had five straight successful years. Not because of any skill on their part, but simply because of randomness. So, observing an investment manager who has been successful for several consecutive years cannot by itself tell you that they are successful - they may just have ridden luck to their results. Moreover, Taleb asserts that these "lucky fools" will be oblivious to the role of luck in their success - a form of what in behavioural economics we refer to as positivity bias (we are overly optimistic about anything to do with ourselves).

There's lots of good stuff on behavioural finance, bounded rationality, etc. in the book, and I especially liked the discussions of inductive reasoning and the work of David Hume; I must admit to not being as familiar with Hume as I probably should be. Probably there's some further reading there for me.

So, even though Taleb argues that he will never read unsolicited comments on his book, I've provided some anyway. And I would recommend this as a good read if you are interested in finance, or if you simply want some good punchlines to use against economists.

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