Fortune's Formula: The Untold Story of the Scientific Betting System That Beat the Casinos and Wall Street

When faced with a choice of wagers or investments, choose the one with the highest geometric mean of outcomes. This rule, of broader application than the edge/odds Kelly formula for bet size, is the Kelly criterion.

Life is short, and the stock market is a slow game. In blackjack, it’s double or nothing every forty seconds. In the stock market, it generally takes years to double your money—or to lose practically everything. No buy-and-hold stock investor lives long enough to have a high degree of confidence that the Kelly system will pull ahead of all others.

You might then ask how LTCM would have been any better off with the Kelly system. The answer is that the Kelly criterion can be more forgiving of human error than many other systems—including highly leveraged approaches such as LTCM’s. Recall the example of simultaneous bets on a large number of coins, each with a 55 percent chance of coming up hea

Within a few years as U.S. Attorney, Giuliani was probably the nation’s best-known crime-fighter since J. Edgar Hoover. That was due both to how many important convictions he secured and to his genius for promoting them. Though Giuliani expanded the U.S. Attorney’s office to 132 assistants, he presented himself as the iconic figurehead of that offi

Meriwether did not himself possess a first-rate mathematical mind. Instead, he recruited the top academic talent. No finance professor was more respected than Robert C. Merton. Merton had consulted for Salomon Brothers, so Meriwether already knew him. He agreed to come on board. Meriwether’s other great coup was recruiting Myron Scholes. As journal

The consumer of VaR reports is led to believe that the numbers are reliable because smart people have gone to a lot of trouble to work them out. The numbers are only as good as the assumptions underlying them.

The best you can do right now is to choose a portfolio with the highest geometric mean of the probability distribution of outcomes, as computed from current means, variances, and other statistics. The returns and volatility of your investments will change with time. When they do, you should adjust your portfolio accordingly, again with the sole obj

Latané called his approach to portfolio design the geometric mean criterion. He demonstrated that it is a myopic strategy. A “near-sighted” strategy sounds like a bad thing, but as economists use it, it’s good. It means that you don’t have to have a crystal ball on what the market is going to do in the future in order to make good decisions now. Th

The Kelly formula says that you should wager this fraction of your bankroll on a favorable bet: edge/odds The edge is how much you expect to win, on the average, assuming you could make this wager over and over with the same probabilities. It is a fraction because the profit is always in proportion to how much you wager. Odds means the public or to