Archive / Investment Adviser (Level 1) / Portfolio Performance Measurement and Evaluation

nism-series-xa-sortino-ratio-vs-sharpe-ratio-when-preferred[ INVESTMENT ADVISER (LEVEL 1) ]

When is the 'Sortino Ratio' preferred over the 'Sharpe Ratio' for evaluating an investment strategy?

[ A ]When evaluating pure index funds with zero tracking error.

[ B ]When the fund manager's tenure is less than 30 days.

[ C ]When the portfolio holds exclusively risk-free sovereign treasury bills.

[ D ]When the portfolio return distribution is asymmetric (skewed) or contains non-linear option payoffs, because Sortino penalizes only Downside Semi-Variance rather than total volatility.[ CORRECT ]

Takeaway

The Sortino Ratio is preferred over the Sharpe Ratio when a strategy's return distribution is skewed or contains option-like payoffs, because Sortino only penalizes downside volatility, not the upside swings that Sharpe unfairly punishes.

Derivation

Sharpe Ratio divides excess return by total standard deviation, treating upside and downside volatility identically — a flaw when returns are asymmetric, since a strategy with large favorable spikes (e.g., a long options overlay) gets penalized by Sharpe for volatility that investors actually welcome. Sortino Ratio instead divides excess return by downside semi-deviation (volatility measured only from returns below a minimum acceptable threshold), so it correctly rewards strategies that generate upside skew while still penalizing genuine downside risk. This distinction is tested because candidates often assume the two ratios are interchangeable, when in fact Sortino is specifically designed for non-normal, skewed return profiles where Sharpe is misleading.

Why the others fail

A — When evaluating pure index funds with zero tracking error.

Passive index funds with zero tracking error are typically judged by tracking error and information ratio against their benchmark, not by downside-risk-adjusted ratios like Sortino.

B — When the fund manager's tenure is less than 30 days.

Manager tenure has nothing to do with which risk-adjusted performance ratio is mathematically appropriate for a given return distribution's skewness.

C — When the portfolio holds exclusively risk-free sovereign treasury bills.

A portfolio of pure risk-free treasury bills has effectively zero volatility on both sides, so there is no meaningful downside-deviation calculation for Sortino to add value over Sharpe.