S&P 500 CAPE Ratio Hits 41 After Consecutive Annual Gains of 26%, 25%, and 18%
Resolved · market structure · Occurred · Assessed · 1 sources
This assessment is dated 2026-09-18. Check what remains unresolved below before relying on it.
What changed relative to expectations?
A CAPE ratio of 41 leaves the S&P 500 multiple vulnerable to mean-reversion derating if higher short-term rates lift discount rates across mega-cap index constituents.
| Question | What the evidence establishes |
|---|---|
| What was reported? | Reported factThe cyclically adjusted price-to-earnings (CAPE) ratio for the S&P 500 has reached 41. |
| What else was confirmed? | Reported factThe S&P 500 posted successive three-year returns of 26%, 25%, and 18%, driven by generative artificial intelligence spending. |
| Does the valuation support acting? | UnknownRequires applying the change to specific holdings. |
| What would change the assessment? | UnknownS&P 500 forward earnings revisions — Consensus S&P 500 EPS estimate trajectory relative to 41 CAPE benchmark |
What would this event cost your holdings?
Apply your own hypothetical returns to current holding values. The calculator does not infer security effects from this event.
Test this event against my holdingsReported facts
- · The cyclically adjusted price-to-earnings (CAPE) ratio for the S&P 500 has reached 41.
- · The S&P 500 posted successive three-year returns of 26%, 25%, and 18%, driven by generative artificial intelligence spending.
- · A CAPE ratio of 41 has occurred only twice in 155 years of historical market records (prior to 1929 and 1999).
Public research record
Research framework · page evidenceCompleted event assessment
index valuation multiple derating pressure
| Type | Claim | Scope |
|---|---|---|
| Assumption | The cyclically adjusted price-to-earnings (CAPE) ratio for the S&P 500 has reached 41. | 2026-09-18 |
| Interpretation | index valuation multiple derating pressure | SPY |
Countercase, invalidators, and sources
Earnings revisions from AI infrastructure deployment accelerate, compressing the multiple through denominator growth.
- · S&P 500 forward earnings revisions — Consensus S&P 500 EPS estimate trajectory relative to 41 CAPE benchmark
- As the Stock Market Flashes a Warning Seen Only 2 Times in 155 Years, Warren Buffett has a Big Warning for Investors · 2026-09-17
What remains unresolved
- Base path
- Equity indices trade in an elevated volatility range as high multiples absorb 5% risk-free rate competition.
- Adverse path
- Margin compression across mega-caps triggers multiple derating toward historical long-term averages.
- Supportive path
- Earnings revisions from AI infrastructure deployment accelerate, compressing the multiple through denominator growth.
- · S&P 500 forward earnings revisions — Consensus S&P 500 EPS estimate trajectory relative to 41 CAPE benchmarkthis week
Evidence
- As the Stock Market Flashes a Warning Seen Only 2 Times in 155 Years, Warren Buffett has a Big Warning for Investors2026-09-17
“The S&P 500 has surged 26%, 25%, and 18% over the last three years, driven largely by generative AI hype. However, the market's CAPE ratio now stands at 41 - a level seen only twice in 155 years (before the dot-com bubble in 1999 and the Great Depression in 1929).”
Supports: S&P 500 gained 26%, 25%, and 18% over the last three years and CAPE ratio reached 41, seen only twice in 155 years.