Sell in May and Go Away: Does It Still Work? 41 Years of S&P 500 Data
We tested the "Sell in May" rule on 41 years of S&P 500 data. Winters beat summers on average — but summers still made money, and recent years broke the rule.
Key takeaways
- From 1985 to 2025 the S&P 500 averaged +7.26% in November–April vs +2.95% in May–October (price index).
- Summers were still positive in 30 of 41 years, so moving to cash usually cost money.
- The weak-summer average is driven by rare crashes such as 2008 (−30.1%).
- Summer beat the preceding winter in 4 of the last 10 years; 2025's summer gained 22.8%.
Short answer: the seasonal gap is real, but "go away" is bad advice. From 1985 to 2025, the S&P 500 rose an average of 7.3% in the November–April half versus 3.0% in May–October (price index, our calculation from Yahoo Finance monthly closes). Yet summers were positive in 30 of 41 years — so sitting in cash through them usually cost money.
What "Sell in May and Go Away" means
The old saying tells investors to sell stocks at the end of April and return around Halloween, on the belief that the six "summer" months deliver weak returns. Academics call the same pattern the Halloween indicator; Bouman and Jacobsen documented it across 36 of 37 markets in a 2002 American Economic Review paper.
The numbers: 41 years of S&P 500 halves
We measured each half-year from month-end close to month-end close (April 30 to October 31, and October 31 to April 30) for 1985–2025. Dividends are excluded, which slightly understates both halves.
| Period | Average | Median | Positive years | $1 compounded |
|---|---|---|---|---|
| May–October | +2.95% | +4.34% | 30 / 41 | $2.68 |
| November–April | +7.26% | +7.25% | 32 / 41 | $14.94 |
The winter half beat the following summer in 28 of 40 year-pairs. On averages alone, the effect is clear — and it matches the calendar pattern we found in crypto for Uptober.
Why "go away" still loses
A weaker half is not a losing half. Summer's median gain of about 4% is roughly what cash has paid in a good year, before taxes and trading costs from switching twice a year. The summer average is also dragged down by a few crashes — May–October 2008 fell 30.1%, 2002 fell 17.8% and 2001 fell 15.2% — so the rule mostly works by dodging rare disasters that nobody can schedule in advance.
The last decade broke the pattern
From 2016 to 2025, summer was positive in 9 of 10 years, and it beat the preceding winter in 4 of them. Summer 2025 gained 22.8% (April 30 close to October 31 close), and 2024 added 13.3%. This year, the S&P 500 closed April 2026 at 7,209.01 and was trading near 7,709 on September 30, 2026 — about +6.9% with a month of the "bad" half still to go.
How traders actually use seasonality
- As a tilt, not a switch. Some trim risk or tighten stops in late summer rather than exiting entirely.
- Combined with trend. Seasonality means little against a strong trend; signals like the golden cross carry more weight.
- With sentiment context. Fear gauges like the put/call ratio help judge whether a seasonal dip is being bought.
You can check current trend readings for the S&P 500 on our technical analysis tool. If you want to act on a view, open a trading account — and size positions for the risk that seasonality simply doesn't show up this year.
Methodology: S&P 500 index (^GSPC) monthly closes from Yahoo Finance, retrieved September 30, 2026; price returns only. Past seasonal patterns do not guarantee future results. This article is educational and is not investment advice.
Sources & methodology
Primary sources and datasets referenced in this article. How we source, verify and date our reporting is set out in our editorial policy & methodology.
- S&P 500 (^GSPC) historical monthly prices— Yahoo Finance · retrieved 30 Sept 2026 · as of 30 Sept 2026Monthly closes 1985–2026 used to compute all half-year returns
- The Halloween Indicator, 'Sell in May and Go Away': Another Puzzle— American Economic Review (Bouman & Jacobsen) · published 1 Dec 2002 · retrieved 30 Sept 2026Original academic study of the effect across 37 markets