Kelly Criterion Calculator 1.2

The Kelly criterion, often referred to as the Kelly strategy or Kelly bet, is a significant concept in probability theory and intertemporal portfolio choice. Originating from the work of J. L. Kelly Jr., a researcher at Bell Labs in 1956, it serves as a formula for bet sizing that systemically leads to greater wealth over the long term, particularly as the number of bets increases indefinitely.

At its core, the Kelly criterion focuses on maximizing the expected value of the logarithm of wealth, which directly correlates with maximizing the expected geometric growth rate. The approach suggests that an individual should wager a specific fraction of their assets, a principle that may initially appear counterintuitive to some.

For instance, when applied to an even-money bet, the calculation for determining the optimal wager size is straightforward: one multiplies the percentage chance of winning by two and then subtracts one. Thus, for a betting scenario with a 70% probability of winning, the prescribed wager would represent 40% of the available funds.

The application of the Kelly criterion extends beyond gambling; it has also influenced strategies in investment management, notably in portfolio diversification. Since the early 2000s, Kelly-style analysis has gained traction within mainstream investment theory. Notable investors like Warren Buffett and Bill Gross have been associated with employing Kelly methods in their strategies. Furthermore, William Poundstone has provided a comprehensive account of the historical context surrounding Kelly betting, offering valuable insights into its evolution and significance in both gambling and finance.