It is well known that equity indices tend to exhibit a negative correlation with their volatility. There is some research on this relationship, often linking it to the leverage effect. Recently, we observed that the equity market has been behaving unusually, with the spot-volatility correlation turning positive. It is therefore timely to revisit research on this relationship.
Reference [1] studies how changes in the spot-volatility correlation affect expected option returns. The study uses SPX options from 1996 to 2023, realized variance calculated from 5-minute S&P 500 futures data, and a 30-day rolling return-variance correlation. The authors formulate the research problems using the Heston option pricing model under the physical measure. They pointed out,
This paper examines how the leverage effect affects expected index option returns. We rely on the Heston (1993) stochastic volatility framework and the exponential-affine pricing kernel in Heston et al. (2024b) to characterize the relation between the return-variance correlation and expected index call and put returns…
The theoretical analysis predicts a negative (positive) relation between the market leverage effect and call (put) expected returns, and the magnitudes of these relations increase for out-of-the-money contracts for calls. We confirm these theoretical predictions using a long sample of weekly S&P 500 index option returns. The estimated signs are robust across alternative formation days, the exclusion of expiration weeks, longer maturities, and a monthly holding period aligned with the option expiration cycle, and the results remain statistically significant.
In short, the paper concludes that,
- When correlation increases, i.e., becomes less negative, expected call returns decrease and expected put returns increase. Equivalently, a more negative correlation raises expected call returns and lowers expected put returns;
- For calls, the effect becomes substantially stronger OTM; for puts, it becomes weaker OTM.
This article tackles a relatively underexplored but important topic. An interesting irony is that the correlation can become positive when investors aggressively buy out-of-the-money call options as the equity market rallies, thus increasing volatility and causing the correlation to turn positive. However, by doing so, they also reduce the expected returns on their calls.
Let us know what you think in the comments below or in the discussion forum.
References
[1] Driessen, J., Jeon, J., and Sun, Y. (2026), The Leverage Effect and Expected Option Returns, Working Paper
Article Source Here: Impact of Spot-Volatility Correlation on Option Returns
source https://harbourfronts.com/impact-spot-volatility-correlation-option-returns/