SPY Option Skew, Short-Dated Call Sensitivity, and Volatility of Volatility
Summary
The document addresses how implied volatility can affect short-dated, out-of-the-money SPY calls when SPY rises and market volatility falls. The answer points to the volatility skew: out-of-the-money calls often carry lower implied volatility than at-the-money options, reflecting the typical asymmetry of market moves. As spot rises, a fixed strike moves to a different point on the skew, which can partly offset a broad decline in implied volatility. The answer also says short-maturity calls generally have limited vega, so their price response is more centered on the underlying move than on a short-term volatility change.
For volatility implied by VXX options, the reply distinguishes it from VXX’s own price volatility and calls it volatility of volatility, citing VVIX as an index that tracks this concept. The explanation is brief and qualitative: it offers no option-pricing calculation or historical data, and notes that skew patterns are not universal. A trader would still need to assess the option’s full Greeks, strike, maturity, and prevailing volatility surface.
Key ideas
- Implied volatility varies across strikes, producing a volatility skew in SPY options.
- A rising SPY price can move a fixed strike along the skew and partly offset a general volatility decline.
- Short-dated out-of-the-money calls often have limited vega, making spot movement a major source of price sensitivity.
- Implied volatility of VXX options represents volatility of VXX rather than VXX’s own price volatility.
- VVIX is cited as an index that tracks volatility of volatility, while skew patterns can vary across conditions.
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# Basic questions on options, implied volatility and SPY # Basic questions on options, implied volatility and SPY I am a bit confused about the impact of implied volatility on options, SPY options especially. I know that option's price decays with time and that is positively correlated with implied volatility but here some questions: - Question #1: Because implied volatility seems to be highly correlated with actual volatility (i.e. VXX) in the market (at least over a timescale of weeks) and because VXX is negatively correlated with SPY, buying a short-term (i.e. 10-day) OTM call on SPY seems to be a loosing bet most of the time: If SPY goes up, your call might go up in price because it is closer to the striking price but that increase might be eliminated by the decrease in implied volatility. So, what I am missing here? - Question #2: How should I understand the implied volatility of VXX itself? Is it just correlated with VXX or a completely different beast? (I could not find any historical data on VXX's implied volatility.) Disclaimer: I have been learning about options only over the last 2 weeks so, I apologize if these questions look dumb. ## Answer by Lliane (score 4, accepted) https://quant.stackexchange.com/a/43009 - 1 : You are describing one of the reasons of the volatility skew : generally, implied volatility on an OTM SPY call will be lower than ATM (which in turn is lower than ITM) for this reason. Indeed, the magnitude of upside moves is generally lower than downside moves so your call is cheaper for this reason. Note that it is not always the case. Note also that as the spot moves up, your strike shifts down on the vol skew towards higher volatilities (which mitigates the vol lost due to "quiet markets"). Also, your 10 day OTM call will probably not have a lot of vega (volatility exposure) because its maturity is so close. You're clearly playing a move of the spot price, not a short term change in the implied vol. - 2 : This is called the vol of vol, there is an index called VVIX which tracks it, and yes it's a completely different beast. It's mostly used for structured/exotic products but there's a lot of research published as academics love it for some reason.
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