Reader’s Diary

William Poundstone

This book is about the “Kelly formula” (explained on the author’s web site) which, despite the book’s subtitle, is not so much a betting system but a money management system for gamblers.  It also applies to stock market investing, which says something about the nature of the market vs. the casino.

The Kelly formula is based on the observation that even a gambler with inside information that gives him a substantial edge – or the investor who succeeds in identifying “inefficiencies” in the market – can go broke if he dumps all his money into a enough bets that don’t turn out as expected.  The formula gives the gambler/investor a way to determine  just how much of his stake to place on each bet/investment. By applying the formula he can maximize his profit at the cost of volatility.  The volatility can be reduced by betting at “less than Kelly”,  a precaution that also allows for errors in the bettor/investor’s estimate of the numbers that are the inputs to the formula.

Poundstone explains the Kelly concept in non-mathematical terms and tells the stories of people who developed it and used it.  In the course of the book he introduces the reader to scientists, gamblers, mobsters, and investment gurus (and charlatans).  The connective thread is the story of  Edward O. Thorp who famously “Beat the Dealer” at blackjack and less famously “Beat the Market“.

All in all, it’s an interesting book taught me a little about a lot of areas I knew little about.  I do wish Poundstone had focused more on the estimates on which the formula depends and on concrete examples of how the average investor – or gambler – might apply the formula.

This entry was posted on Tuesday, April 13th, 2010 at 10:35 pm and is filed under Books, Nonfiction. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.