Coherent Model-Free Implied Volatility: A Corridor Fix for High-Frequency VIX
The VIX index is computed as a weighted average of SPX option prices over a range of strikes according to specific rules regarding market liquidity. It is explicitly designed to provide a model-free option-implied volatility measure. Using tick-by-tick observations on the underlying options, we document a substantial time variation in the coverage which the stipulated strike range affords for the distribution of future S&P 500 index prices. This produces idiosyncratic biases in the measure, distorting the time series properties of VIX. We introduce a novel “Corridor Implied Volatility” index (CX) computed from a strike range covering an “economically invariant” proportion of the future S&P 500 index values. We find the CX measure superior in filtering out noise and eliminating artificial jumps, thus providing a markedly different characterization of the high-frequency volatility dynamics. Moreover, the VIX measure is particularly unreliable during periods of market stress, exactly when a “fear gauge” is most valuable.
References listed on IDEAS
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- Todorov, Viktor & Tauchen, George, 2010.
"Activity signature functions for high-frequency data analysis,"
Journal of Econometrics,
Elsevier, vol. 154(2), pages 125-138, February.
- George Tauchen & Viktor Todorov, 2010. "Activity Signature Functions for High-Frequency Data Analysis," Working Papers 10-08, Duke University, Department of Economics.