How Much Can a Risk Metric Lie?
Measuring the manipulability of ten standard risk and performance statistics.
We test ten widely used risk and performance statistics — including Sharpe, Sortino, Calmar, VaR, expected shortfall and maximum drawdown — against five manipulation attacks: return smoothing, path reordering, reporting-period selection, tail-risk selling and option-based payoff reshaping. A single comparable measure, the manipulation ratio, shows how far each metric can be pushed, while a manipulation-proof control ensures no attack delivers any genuine economic improvement. The report ranks the metrics from most to least exploitable and tests real ETF returns for hidden smoothing.
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