(Excerpt from A Man for All Markets by Ed Thorp)
Kelly’s criterion is not limited to two-value payoffs but applies generally to any gambling or investing situation in which the probabilities are known or can be estimated.
Some key features of the Kelly Criterion are: (1) The investor or bettor generally avoids total loss; (2) the bigger the edge, the larger the bet; (3) the smaller the risk, the larger the bet.
… Three caveats: (1) The Kelly Criterion may lead to wide swings in the total wealth, so most users choose to bet some lesser fraction, typically one-half Kelly or less; (2) for investors with short time horizons or who are averse to risk, other approaches may be better; (3) an exact application of Kelly requires exact probabilities of payoffs such as those in most casino games; to the extent these are uncertain, which is generally the case in the investment world, the Kelly bet should be based on a conservative estimate of the outcome.
… He and his associate Charlie Munger, when managing $200 million, put most of it into just five or so positions. Sometimes he was willing to bet 75 percent of his fortune on a single investment. Investing heavily in extremely favorable situations is characteristic of a Kelly bettor.