SPX sessions closed in positive gamma, with the net-gamma percentile 80 and above, on expiration days
19 sessions · the archive filtered by the dealer book · all sessions · the calendar
19 of 1,122 sessions match. Of them 100% closed above the flip (archive 56%) and the mean open-to-close move was 0.63% (archive 0.59%).
Every row is a finished SPX session and links to its page, where the same numbers stand with the day's events and a free minute-by-minute replay. The filters are the closing measurements those pages print: the zero-gamma flip against the close and the open, the net-gamma percentile, how often the flip was crossed, and the calendar event the day carried. The shares above are counts over the matched days next to the same counts over the whole archive; a share that matches the archive is a base rate, not a pattern.
| Session | Close | Move | Flip | vs flip | Pctl | Cross | Events |
|---|---|---|---|---|---|---|---|
| 2026-09-18 | 7,648.15 | +0.09% | 7,630.0 | +18.1 | 95 | 22 | Opex |
| 2026-08-31 | 7,685.95 | -0.06% | 7,677.5 | +8.5 | 80 | 40 | Opex |
| 2026-02-27 | 6,879.27 | +0.43% | 6,859.8 | +19.5 | 95 | 10 | PPI, Housing, Opex |
| 2026-02-20 | 6,909.09 | +1.06% | 6,895.8 | +13.3 | 100 | 6 | PCE, GDP, UMich, Housing, Opex |
| 2025-11-28 | 6,848.69 | +0.04% | 6,832.4 | +16.3 | 100 | 1 | UMich, EIA, Opex |
| 2025-09-19 | 6,664.50 | +0.30% | 6,650.3 | +14.3 | 90 | 9 | Opex |
| 2025-05-30 | 5,909.25 | +0.27% | 5,886.8 | +22.5 | 80 | 19 | PCE, Opex |
| 2025-05-16 | 5,958.37 | +0.64% | 5,932.1 | +26.3 | 95 | 3 | Housing, Opex |
| 2025-03-21 | 5,667.20 | +0.83% | 5,639.9 | +27.3 | 95 | 18 | Opex |
| 2024-11-29 | 6,035.72 | +0.51% | 6,027.1 | +8.6 | 100 | 0 | EIA, Opex |
| 2024-08-30 | 5,650.20 | +0.57% | 5,609.7 | +40.6 | 85 | 6 | PCE, Opex |
| 2024-05-17 | 5,302.40 | +0.02% | 5,296.9 | +5.5 | 80 | 34 | Opex |
| 2023-11-17 | 4,513.91 | +0.09% | 4,511.5 | +2.4 | 85 | 24 | GDP, Housing, Opex |
| 2023-08-18 | 4,369.62 | +0.62% | 4,363.5 | +6.1 | 80 | 27 | Opex |
| 2022-11-18 | 3,966.55 | -0.32% | 3,953.8 | +12.8 | 85 | 12 | Opex |
| 2022-10-21 | 3,753.64 | +2.73% | 3,713.1 | +40.6 | 85 | 17 | Opex |
| 2022-09-16 | 3,874.41 | +0.45% | 3,859.4 | +15.0 | 85 | 11 | Opex |
| 2022-06-24 | 3,912.02 | +2.14% | 3,878.5 | +33.5 | 85 | 0 | Housing, UMich, Opex |
| 2022-05-20 | 3,903.52 | -0.79% | 3,864.4 | +39.1 | 85 | 9 | Opex |
Turn a filter into a rule
A count is where a question starts. The Lab takes a rule in plain
words ("sell the 0DTE straddle at 10:00 on days that opened below the flip with the
percentile under 20"), compiles it against every archived session and reports the
out-of-sample verdict with day-clustered intervals. An assistant with the
MCP server can page through the same archive with
list_sessions and get_session.
Measurements are model output derived from public trade and quote data; they are approximations and can be wrong. Nothing here is investment advice; see the Terms.