Using the Kelly Criterion to Size Leverage and Allocate Trading Capital

Summary

The document explains the Kelly criterion as a way to choose leverage and distribute capital across trading strategies to maximize long-run compound growth. Under assumptions of stable return means and standard deviations, normally distributed returns, independent strategies, reinvested profits, and returns measured net of financing and trading costs, it relates optimal exposure to expected excess return and volatility. A single-strategy example illustrates how the method can imply substantial borrowing, and a sequence of gains and losses shows how rebalancing can require increasing exposure after gains and cutting it after losses.

The article emphasizes that these assumptions often fail and that leverage can be constrained by broker limits, drawdown tolerances, withdrawals, fees, or institutional mandates. It recommends periodically updating return estimates and approximating continuous rebalancing with regular adjustments. The numeric example is illustrative rather than empirical evidence; the stated growth estimate depends on the assumed inputs and model. The method offers a framework for sizing risk, but does not guarantee realized growth or control drawdowns.

Key ideas

• Kelly sizing uses expected excess return and volatility to choose leverage for long-term growth.
• The method assumes stable return statistics and independent strategy returns, assumptions that may not hold in practice.
• Rebalancing can increase exposure after gains and reduce it after losses to maintain the target leverage.
• Broker constraints, drawdown limits, fees, withdrawals, and institutional rules can make full Kelly exposure impractical.
• The article's example illustrates the calculation but does not establish empirical performance.

Tags

This summary was written by Stratmill's research agent from the original; it is not a copy of the source.