Beginner
What It Means
The Treynor Ratio tells you how much return you’re getting for each unit of market risk (beta) you’re taking. Unlike the Sharpe Ratio which uses total volatility, Treynor only considers systematic risk.Portfolio Example
*Assuming 2% risk-free rate
Portfolio B is better - generating more return per unit of market risk taken, despite lower absolute returns.
When to Use It
Best for evaluating well-diversified portfolios where unsystematic (stock-specific) risk has been eliminated through diversification. If your portfolio is well-diversified, beta is what matters most.Why It Matters
If your portfolio is part of a larger, diversified allocation, the Treynor Ratio tells you if you’re being compensated fairly for market exposure. Unsystematic risk can be diversified away, so only systematic risk matters.Advanced
Mathematical Definition
Historical Context
Developed by Jack Treynor (1965), one of the developers of CAPM alongside Sharpe, Lintner, and Mossin. While less famous than the Sharpe Ratio, it provides complementary insights for portfolio evaluation.What Makes It Useful
- Focus on Systematic Risk: For well-diversified portfolios, only systematic risk matters
- Complements Sharpe Ratio: Sharpe uses total risk (σ), Treynor uses systematic risk (β)
- Portfolio Comparison: Compare portfolios with different diversification levels
- Theoretical Foundation: Direct link to CAPM expected return framework
Sharpe vs. Treynor: Key Insight
Data Requirements
Treynor Ratio reliability depends entirely on beta estimation quality. Beta instability makes Treynor Ratio time-varying.
When Treynor is Better Than Sharpe
When Sharpe is Better Than Treynor
Limitations
- Assumes Good Diversification: Misleading for concentrated portfolios with significant idiosyncratic risk
- Beta Limitations: Inherits all limitations of beta (time-varying, single-factor, etc.)
- Less Intuitive: Denominator (beta) is more abstract than volatility
- Limited Usage: Less common in practice than Sharpe Ratio
Alternatives
Related Terms
Beta
The denominator of Treynor
Sharpe Ratio
Uses total risk instead
Alpha
Related performance measure