Calming “expensive protection” arbitrage opportunities in the US stock market: Faxin suggests selling short-term tail fluctuations, but it is necessary to hedge against the risk of a sharp decline

The Zhitong Finance App learned that Société Générale strategists said that the recent rise in short-term option premiums in the S&P 500 index has created potentially attractive opportunities for investors willing to sell volatility, provided they hedge against the risk of a sudden market decline.

According to a report released by the bank's cross-asset quantitative research team on September 4, the current price of options with one or two days until the expiration date reflects a fluctuation far greater than usual, whether it is rising or falling. Since mid-August, this change has been particularly evident, although the actual volatility (that is, the magnitude of actual market fluctuations) is still relatively moderate.

This gap means that traders who sell “tail swing” options (that is, hold options to hedge against extreme market fluctuations) may be more compensated for the risks they take. Société Générale has listed this strategy as one of its preferred volatility arbitrage trading strategies.

For investors, the proposal highlights an important difference between a calm market and low-cost hedging protection. Stock prices may not fluctuate drastically, but options traders charge higher fees to avoid the risk of a sudden rise or fall in the market. This may benefit volatility sellers, but if the market suddenly breaks through the recent fluctuation range, gains may also be accompanied by serious losses.

The bank's analysis found that since mid-August, the implied downside risk of two-day put options in the S&P 500 index has increased compared to the realized volatility. At the same time, the implied upward risk of similar bullish options has also increased, thereby boosting both ends of the market's implied probability distribution.

Société Générale warned that selling such short-term options would pose a huge negative gamma risk. In effect, this means that when stock prices fluctuate drastically, especially during periods of rapid market declines, the strategy may accelerate losses.

To mitigate this risk, the bank tends to combine this deal with its “synthetic downward variance” strategy. This strategy is a stock volatility hedging tool designed to benefit from major shocks. The report shows that the hedging strategy performed strongly during the outbreak of market volatility in February 2018, the stock market crash caused by the pandemic, and the sell-off wave caused by tariffs in 2025.

These two strategies are meant to complement each other: short-term late-term volatility positions usually charge a premium when the market is calm, and hedging strategies can generate profits when sudden sell-offs cause losses in volatile sell trades.

However, this protection is not perfect. A rapid decline in the market may cause losses to short-term positions before long-term implied volatility rises enough to hedge profits. Conversely, in a gradual, long-running bear market like 2022, hedging strategies may struggle — and this environment may be more conducive to short-term volatility strategies.

The strategists also warned investors not to expect government bonds to reliably offset stock market losses. They believe that high and unstable interest rates are a core macroeconomic risk and may weaken the traditional negative correlation between stocks and bonds. Therefore, the bank tends to adopt a clear stock volatility strategy to protect the stock market and hold long-term volatility positions to hedge interest rate risks.