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The Sharpe Ratio tells you how much return you’re getting for each unit of risk you’re taking. It’s the most widely used measure of risk-adjusted performance in the investment industry.

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Beginner

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What It Means

The Sharpe Ratio measures “bang for your buck” in terms of risk. Higher is better - you’re getting more return for each unit of volatility you endure.

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Portfolio Example

PortfolioReturnVolatilitySharpe Ratio*
Portfolio A12%8%1.25
Portfolio B15%15%0.87
*Assuming 2% risk-free rate Even though Portfolio B has higher returns, Portfolio A is better on a risk-adjusted basis. You’re getting more reward per unit of risk.

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Why It Matters

It helps you compare different investments fairly. A 20% return with 30% volatility isn’t necessarily better than a 12% return with 8% volatility. The Sharpe Ratio reveals which investment is truly more efficient.

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Advanced

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Mathematical Definition

Sharpe Ratio = (Rp - Rf) / σp

Where:
- Rp = Portfolio return
- Rf = Risk-free rate (typically 3-month T-bills)
- σp = Portfolio standard deviation (total volatility)

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Historical Context

Developed by William Sharpe (1966), originally called the “reward-to-variability ratio.” It became the industry standard for risk-adjusted performance measurement. Sharpe received the 1990 Nobel Prize partly for this contribution.

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Interpretation Benchmarks

For long-only equity strategies (annualized):
Sharpe RatioInterpretation
< 0Portfolio underperforming risk-free rate
0 to 0.5Below average risk-adjusted returns
0.5 to 1.0Good risk-adjusted performance
1.0 to 1.5Very good risk-adjusted performance
> 1.5Excellent (rare over multi-year periods)
Strategy-Specific Benchmarks:
  • Long-only equity: SR 0.5-1.0 typical, >1.5 excellent
  • Long/short equity: SR 1.0-2.0 good, >2.5 excellent
  • Market-neutral: SR >2.0 achievable but rare over multi-year periods

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What Makes It Useful

  • Universal Comparability: Can compare across any asset classes or strategies
  • Intuitive Interpretation: Simple ratio that captures risk-return tradeoff
  • Portfolio Optimization: Maximizing Sharpe Ratio leads to optimal risk-adjusted portfolios
  • Performance Evaluation: Standard metric for evaluating fund managers and strategies

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Data Requirements

RequirementDurationNotes
Minimum36 months (3 years)Basic Sharpe Ratio estimate
Preferred60-120 months (5-10 years)Stable, meaningful comparisons
Statistical Confidence:
  • Sharpe = 0.5 needs ~4 years to be statistically different from zero
  • Sharpe = 1.0 needs ~2 years to be statistically significant
Short-period (less than 2 years) Sharpe Ratios are essentially noise. Bull vs. bear markets dramatically affect estimates.

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Limitations

  • Assumes Normal Distribution: Real return distributions have fat tails and skewness; Sharpe Ratio doesn’t capture this
  • Symmetric Risk Treatment: Treats upside and downside volatility equally, but investors care more about downside
  • Time Period Sensitive: Can vary significantly based on measurement period
  • Gaming Potential: Can be artificially inflated through return smoothing or option writing strategies

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Alternatives

AlternativeUse Case
Sortino RatioUses downside deviation instead of total volatility, focusing on harmful volatility
Calmar RatioReturn over maximum drawdown, captures tail risk better
Information RatioFor active strategies, measures excess return per unit of active risk
Omega RatioProbability-weighted ratio of gains vs. losses above/below threshold

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Related Terms

Standard Deviation

The denominator in Sharpe Ratio

Information Ratio

Active management version

Treynor Ratio

Uses beta instead of volatility