How Option Dealer Hedging Can Amplify or Dampen Stock Moves
Summary
The document explains how option market makers’ delta hedging can transmit options positioning into the underlying stock. When dealers are short options held by customers, rising prices may require them to buy shares and falling prices to sell, reinforcing existing moves. When dealers are net long options, the hedge can instead involve buying dips and selling rallies, which may damp price swings.
The effect is described as conditional rather than a fixed property of a stock: it depends on which side of the options trades dealers hold, as well as the option strikes and time to expiry. Hedging pressure is expected to be strongest when many options are near expiry and the stock is near their strike. The discussion is a conceptual explanation, not an empirical ranking of stocks or a quantified estimate of how much returns are driven by options activity.
Key ideas
- Dealer delta hedging can connect options positioning to buying or selling in the underlying stock.
- Dealers short options may hedge in ways that reinforce price moves and volatility.
- Dealers long options may hedge in ways that damp rallies and declines.
- Hedging effects may be strongest near expiry when spot is close to heavily traded strikes.
- The direction of the effect depends on the net options positions dealers must hedge.
Tags
Full text
# What kind of stock's prices are most affected by option trading? # What kind of stock's prices are most affected by option trading? Option trading translates into stock trading via market maker hedging. For instance, if I buy a call option, the market maker will have to buy the stock to delta hedge. Thus, this should translate into an upward pressure on the stock's prices. I imagine that the impact of option trading is larger on some stocks than others (in causing price movements). For instance, for some stocks, option trading may account for 10% of return variance, but for others the number may be close to zero. What kind of stocks would have a higher fraction of returns caused by option trading, in your mind? ## Answer by demully (score 1) https://quant.stackexchange.com/a/60788 This question reminds me of, many moons ago in a galaxy far far away, the third week of every third month, when the pointyheads who think "vega" is a real word used to start talking about "pin risk" [or "the gamma hammer", if they wanted non-derivative grunts who don't think in Greeks to shut up and listen]. The punchline being that it matters what options the punters have traded vs the banks. Whether they are long or short options (of either type) close to the strike close to expiry. If the punters are net long of calls and/or puts versus their banks, then the banks are thus on the short side of these trades. If the market rises, the banks have to buy to maintain their delta hedge. If the market falls, then the banks will sell. Adding to pre-existing price pressures thus will tend to pro-cyclically encourage market volatility. But if the punters are net short of options at that strike, then the opposite applies. Maintaining the hedge will cause the banks to buy the dips, and sell the rallies. Which will tend to suppress market volatility. All of these effects are (hopefully) obviously most extreme if/when the date is close to expiry, and spot is close to the strike on a glut of options. But the effect then is conditional on the mix of options that investors have traded, versus their banks have to hold. This can then have opposing effects, on the incentive for/against volatile momentum effects in the underlying.
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This summary was written by Stratmill's research agent from the original; it is not a copy of the source.