Why Volatility Index Weights Alone Do Not Establish Forecasting Power

Summary

The document asks whether alternative component weighting schemes can improve a volatility index’s forecasts of realized volatility. The question describes a simple trade-weighted emerging-market index that was highly correlated with the VIX over a stated historical interval, while its predictive performance remained under analysis. It also raises criticism of the VIX methodology and asks whether alternatives may be more effective.

The answer cautions that component weights alone do not create forecasting skill, and that correlation with the VIX is not evidence of useful predictive power. It also argues that market conditions and the usefulness of weights can change over time, encouraging analysis beyond construction details. These are general cautions rather than a comparison of specific weighting methods. No forecasting results or supporting tests are provided, so the document does not identify a best scheme. Evaluation requires testing realized-volatility forecasts directly and accounting for changing market behavior.

Key ideas

• A weighting scheme alone does not guarantee stronger realized-volatility forecasts.
• Correlation with the VIX does not demonstrate predictive power.
• Market dynamics and useful component weights may change over time.
• Compare schemes using direct forecasting tests rather than index correlation alone.

Tags

# Volatility Index Weighting Scheme


# Volatility Index Weighting Scheme












Among the several weighting schemes used for constructing volatility indices, which ones are the best for forecasting (realized) volatility? I've constructed a volatility index for emerging markets using a (very simple) trade-weighted approach, which has 84% correlation with the VIX (2007-2012). The construction procedure is much more simple, and I'm still running my regression analysis, so I can't say yet which one has better predicting power.

After reading some articles I've seen lots of critics to the VIX methodology. Is the VIX methodology the best one or there are competitive alternatives for weighting schemes?

TY

## Answer by Matt Wolf (score 2)

https://quant.stackexchange.com/a/6987

Just couple points to ponder about:

- Weighting schemes are not a magic bullet and none of them in isolation will give you higher predictive power (aka. edge). Do not rely on how you weigh components.

- Why would you want to be highly correlated with VIX? Its a poorly constructed index and I find the whole rational behind the implementation details quite questionable. VIX has a very low predictive power.

- Markets are dynamic, most surely weights change, predictive power changes as everything else does: I encourage you to look a lot deeper than just how index components are weighted.

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