Average Monthly Path
Average October finishes +0.73%; this one is +0.90% after 21 sessions.
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The average intra-month path for the S&P 500 and Nasdaq 100 — every occurrence of a calendar month re-based to the prior month-end and averaged by trading day — with the current month drawn on top. Monthly seasonality usually collapses to one number per month; this shows WHEN in the month the return actually arrives. Includes a split-half stability test that flags which of the twelve shapes replicate (December +0.84) and which do not (May -0.82), plus the turn-of-month table, where the first three sessions average roughly 3x a normal day.
- October average path for SPX over 76 years, with 2026 overlaid.
- Average October finishes +0.73%; this one is +0.90% after 21 sessions.
- Split-half r -0.58 — the shape does not replicate.
When to run this study
Run at the start of a month for the shape ahead, or mid-month to see whether the current month is tracking or fighting its usual path. Most useful for timing an entry you have already decided on — the turn-of-month table is the actionable part. Check the stability column before leaning on any single month, since several of the twelve have shapes that do not replicate across halves of the sample.
Historical results
October day by day — cumulative from prior month-end
| Trading day | SPX avg | Median | Win rate | Years | NDX avg | This year |
|---|---|---|---|---|---|---|
| 1 | 0.08 | 0.02 | 53 | 76 | -0.03 | 0.19 |
| 2 | 0.20 | 0.22 | 58 | 76 | -0.27 | 0.93 |
| 3 | 0.47 | 0.64 | 64 | 76 | 0.12 | 1.60 |
| 4 | 0.59 | 0.72 | 63 | 76 | 0.15 | 2.19 |
| 5 | 0.55 | 1.01 | 66 | 76 | -0.23 | 1.96 |
| 6 | 0.65 | 1.03 | 66 | 76 | -0.16 | 1.49 |
| 7 | 0.41 | 0.88 | 68 | 76 | -0.34 | 2.09 |
| 8 | 0.42 | 0.71 | 64 | 76 | -0.25 | 2.03 |
| 9 | 0.71 | 1.21 | 64 | 76 | 0.38 | 2.01 |
| 10 | 0.72 | 1.31 | 61 | 76 | 0.69 | 0.88 |
| 11 | 0.75 | 1.39 | 64 | 76 | 0.84 | 1.21 |
| 12 | 0.84 | 1.50 | 66 | 76 | 0.89 | 0.10 |
| 13 | 0.49 | 1.39 | 64 | 76 | 0.35 | 0.51 |
| 14 | 0.81 | 1.17 | 67 | 76 | 0.81 | 0.80 |
| 15 | 0.84 | 1.26 | 62 | 76 | 1.25 | 1.38 |
Showing 15 of 21 rows — see the live version for all.