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Interpreting Implied Correlation Skews as Market Stress Signals

Article Quant Q&A · Author: Sebastien Wdowiak
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Summary

The document explains implied correlation as a measure of how closely investors expect the assets in an index or portfolio to move together. It distinguishes correlation indices, which can be calculated from index and constituent options, from correlation options themselves. Higher implied correlation is associated with periods of market distress, when asset returns are expected to become more aligned.

It also discusses the shape of implied correlation across option deltas. Elevated implied correlation for out-of-the-money puts can reflect concern that a downturn will involve broad, systemic losses, making it a possible sentiment signal. The cited historical example shows implied correlation rising sharply during the COVID downturn, with a high-delta measure reaching one. The discussion is qualitative and does not establish that correlation skew predicts future returns; it also cautions that a volatility smile should not be mistaken for an implied correlation skew.

Key ideas

  • Implied correlation measures expected co-movement among assets in an index or portfolio.
  • A correlation index can be derived from index and constituent option prices without trading correlation options.
  • Implied correlation tends to rise during periods of market distress.
  • High implied correlation for out-of-the-money puts can reflect expectations of systemic downside risk.
  • A correlation skew may offer sentiment information, but the example does not establish predictive power.

Tags

OptionsEquitiesVolatilitySentiment
Full text
# Implied correlation smile


# Implied correlation smile












i'm currently reading the book of S.BOSSU ADVANCED EQUITY DERIVATIVES. He is currently speaking about the implied correlation smile.

My question is : is it a sentiment indicator as the volatility smile or the correlation option market is too small and there is no feedback effect for this space ? And the excess in correlation in fixed strike are a leading indicator ?

Many thanks

## Answer by AKdemy (score 2, accepted)

https://quant.stackexchange.com/a/80812

There are no correlation options used in computing the correlation index. You already linked the paper, which shows it simply uses index options and options of the constituents (50 tracking portfolio stocks with adjusted weights to be precise).

At the end of the paper can see the big spike around COVID. That holds generally though and a higher implied correlation means that the market expects the individual stocks in an index (or assets in a portfolio) to move more closely together, often in the same direction. That is usually the case in times of distress.

What the index itself will not show (and I am also not sure your figure 8.1 displays) is a correlation skew. I don't know the book but it looks like a standard IV and also does not state it's implied correlation.

In any case, higher implied correlations for out-of-the-money (OTM) put options suggests investors expect that in a market downturn, stocks will be highly correlated, which in turn can indicate bearish sentiment and fear of systematic risks.

https://cdn.cboe.com/resources/indices/documents/Cboe_USO_ImpliedCorrelation_0421_v2.0.2.pdf has a graph showing the historical implied correlations for various deltas. As you can see, the 90 delta implied correlation was 1 during the COVID downturn and the CBOE document also states that

> 90 delta Implied Correlation, for example, quantifies investor expectations about the likelihood of negative systemic shocks

Shown in full with attribution under the source's licence. Licence: CC BY-SA 4.0 (Stack Exchange)

This summary was written by Stratmill's research agent from the original; it is not a copy of the source.