What a Volatility Index Captures Versus Option Implied Volatility

Summary

The document distinguishes a broad implied volatility index from implied volatility values used to analyze individual options. Taking the VIX as an example, the response describes it as summarizing a roughly 30-day volatility measure derived from out-of-the-money calls and puts. That aggregate reading does not show how implied volatility varies across option strikes or expiration dates, so it cannot replace the full volatility surface when examining particular contracts.

The response also notes that implied volatility depends on the pricing model used to infer it. A value backed out using the Black-Scholes formula can differ from one inferred under a jump-diffusion model, particularly when pricing short-dated options. The explanation is conceptual and does not provide equations, data, or a comparison of model estimates. Its central limit is that an index is a useful summary, while contract valuation may require strike-, maturity-, and model-specific analysis.

Key ideas

• A volatility index summarizes a defined slice of option-implied volatility rather than every contract.
• The VIX is described as reflecting a 30-day measure from out-of-the-money calls and puts.
• Option implied volatility varies across strikes and maturities, information an index does not fully represent.
• The pricing model used to infer implied volatility can change the estimate, especially for short maturities.

Tags

# implied volatility indice and implied volatility


# implied volatility indice and implied volatility












Can anybody explain to me Why should we calculate implied volatility if there is already an implied volatility index where implied volatility is already calculated??? I can't understand the difference

## Answer by alexbougias (score 4)

https://quant.stackexchange.com/a/43235

Assuming that you imply that the corresponding volatility index is VIX, it's value represents the 30day IV using the out-of-the-money puts and calls. However, it doesn't capture the structure of the IV for different strikes and maturities. Secondly, depending on the model, we might extract different IV from the IV implied by the BS formula. For instance, under a jump-diffusion model we would extract different IV if we need to price short-term options.

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