Cross-Market Gamma Analysis
Equity index gamma is spread across several venues and products. Looking at one in isolation gives an incomplete picture; comparing them gives you a confidence score for the level you are about to trade.
Normalising across products
SPX, SPY and /ES track the same underlying with different multipliers and strike spacing. Convert every profile to index points and to notional dollars before comparing, otherwise SPY's 1-point strikes look denser than they economically are.
Agreement is a confidence score
When the SPX flip, the SPY flip and the /ES flip cluster within a few index points, the level is robust and worth trading aggressively. When they scatter, the estimate is fragile — size down and demand more confirmation.
- Cluster within ~0.15% of spot: high-confidence level.
- Scattered flips: reduce size and widen stops, or stand aside.
- Futures gamma leads in overnight sessions when the cash chains are closed.
QQQ vs SPY divergence
A negative-gamma QQQ with a positive-gamma SPY typically means tech-specific flow is driving the tape. Expect trend behaviour in NDX names and mean reversion in the broad index — trade each with its own playbook rather than averaging them.
Overnight and session handoff
Use /ES gamma to frame the overnight range, then re-anchor to cash profiles at the open. The most common cross-market trap is carrying an overnight futures level into a cash session that has repriced its entire chain.
A worked cross-check
Suppose SPX shows a flip at 5,090, SPY (adjusted by its roughly 1:10 ratio) implies a flip near 509.2, and /ES shows a flip at 5,093 — all within about three index points of each other with spot trading at 5,110. That tight cluster, within roughly 0.15% of spot, is a high-confidence read: a trader can size a position at or near their normal allocation when trading a break of that zone. Contrast that with a session where SPX implies 5,090, SPY implies 5,070 equivalent, and /ES implies 5,130 — a scatter of 40+ points. That disagreement usually means one product's open interest is temporarily distorted, for example by a single large block trade in SPX options that has not yet been mirrored in SPY flow, and the correct response is to cut size by half or more until the products converge again.
- A cluster within roughly 0.15% of spot across SPX, SPY and /ES supports normal position sizing.
- A scatter of 40+ index points usually reflects a temporary distortion in one product's open interest.
- When in doubt, size to the most conservative (least favorable) of the disagreeing levels, not the average.
Key takeaways
- Normalise to index points and notional before comparing products.
- Clustered flip levels mean high confidence; scattered ones mean stand down.
- Futures lead overnight; cash chains take over at the open.
- When cross-market levels disagree, size to the most conservative level rather than averaging them.
Practice this in the terminal
FAQ
Why would SPX and SPY gamma ever disagree meaningfully?
They share the same underlying but not identical option flow — institutional block trades often concentrate in SPX due to cash settlement and tax treatment, so a large SPX-only trade can temporarily distort its profile relative to SPY before the broader market adjusts.
Is /ES gamma reliable during the regular cash session?
It is most useful overnight and around the open when cash index chains have low liquidity. Once the cash session is running with full volume, SPX and SPY chains generally provide a cleaner and more liquid read than futures options.
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Educational content only. Options involve substantial risk and are not suitable for every investor. Nothing here is financial advice.