Gamma Is Why a Hedge That Worked Yesterday Stops Working
Delta tells you your exposure right now. Gamma tells you how fast that exposure is about to change, which is the part that hurts.
The Second Order Problem
Delta tells you how much an option value moves when the underlying moves a dollar. Gamma tells you how much that delta itself changes over the same move.
If a call has 0.50 delta and 0.05 gamma, then after the stock rises a dollar the delta is roughly 0.55. Rise another dollar and it goes to about 0.60. Your exposure grows as the position works and shrinks as it fails.
This sounds like a technicality. It is the difference between a hedge that holds and a hedge that unravels.
Why It Bites the Seller
Consider a desk that sold a call and bought shares to neutralise the delta. The book is flat. Then the stock rallies.
The call delta rises, so the short option position now represents more negative exposure than the shares offset. The desk is under hedged and losing money. To fix it, it buys more shares, at a price higher than before.
Now the stock falls back. The call delta drops, the desk is over hedged, and it sells shares at a price lower than where it bought them. Repeat this and the desk has been mechanically buying high and selling low, one adjustment at a time.
Being short gamma means every rebalance is a small forced loss. The option premium collected up front is payment for accepting exactly that.
The Long Side
A trader who owns options is long gamma, and the same mechanic runs in reverse. As the stock rises the position gains delta, so they sell shares into strength. As it falls they buy weakness. Each rebalance locks in a small profit.
Nothing is free here. Long gamma costs time decay, paid every day the position exists. The gamma trade is a bet that realised movement will exceed what the option cost.
Where Gamma Concentrates
Gamma is largest for options near the strike price and close to expiry. Far from the strike, delta is stuck near 0 or near 1 and barely moves. Near the strike with days remaining, delta can swing from 0.30 to 0.70 on a modest move.
This concentration is why the final days before expiry are the most difficult to manage. The same one dollar move that mattered little a month ago now flips the entire position.
| Distance from strike | Gamma | Hedging burden |
|---|---|---|
| Far out of the money | Low | Minimal |
| Near the strike | High | Constant adjustment |
| Deep in the money | Low | Minimal |
When It Escapes the Desk
Aggregate dealer positioning turns this into something visible at the index level. When dealers are collectively short gamma, their hedging requires buying as prices rise and selling as prices fall. That is momentum, added mechanically on top of whatever the market was already doing.
When dealers are long gamma, the flow runs the other way and dampens moves. The same hedging discipline either suppresses or amplifies volatility depending on which side the industry sits.
This is why positioning gets discussed as a market condition rather than a private accounting detail. It changes how the market responds to news.
The Practical Reading
Short gamma is a position that is fine until it is not. It generates steady income in quiet conditions and takes concentrated losses in fast ones. The profit and loss profile looks stable right up to the point it stops looking stable, which is exactly the shape that fools risk systems built on recent history.
The Bottom Line
Gamma measures how quickly your exposure changes underneath you. Short gamma means rebalancing at bad prices and collecting premium as compensation. Long gamma means rebalancing at good prices and paying time decay for the privilege. Scaled across an industry, it stops being a hedging detail and becomes a force acting on the market itself.