+1 sessions
Median return +0.50%Completed observations: 35
- Middle 50%
- -0.88% … +1.90%
- Positive returns
- 69%
KLA Corporation · Sigma Moves
Closed-period price moves, measured against their own history. One engine. Five markets. No forecasts.
Latest closed period
KLA Corporation's latest move against its own history.
KLAC Exceptional
-8.42%
-4.29σ
4 times in 5 years
4 comparable moves / 1,255 observations
Small historical sample What happened afterwards
All history-qualified moves of at least 2.5σ. Results after the event are descriptive statistics, not trading instructions.
+7 sessions
Median return +1.35%Completed observations: 35
- Middle 50%
- -1.29% … +6.39%
- Positive returns
- 66%
+30 sessions
Median return +5.81%Completed observations: 35
- Middle 50%
- -4.69% … +14.55%
- Positive returns
- 69%
Every rare move, in context
Instrument: KLAC (price return)
| Date | σ | Move | Observed rarity | +1 sessions | +7 sessions | +30 sessions |
|---|---|---|---|---|---|---|
| 15 Aug 2025 | -4.29σ | -8.42% | 4 times in 5 years4 comparable moves / 1,255 observations | +0.97% | +1.50% | +21.62% |
| 31 Jul 2025 | -2.88σ | -4.97% | About once every 60 trading sessions21 comparable moves / 1,255 observations | +0.87% | +3.54% | +9.67% |
| 22 Jul 2025 | -3.08σ | -4.86% | About once every 78 trading sessions16 comparable moves / 1,255 observations | +0.55% | -1.48% | -5.42% |
| 9 Apr 2025 | +4.44σ | +17.31% | 3 times in 5 years3 comparable moves / 1,256 observations | -6.62% | -11.73% | +9.13% |
| 3 Apr 2025 | -4.60σ | -9.53% | 2 times in 5 years2 comparable moves / 1,256 observations | -7.13% | +7.92% | +27.44% |
| 27 Feb 2025 | -2.77σ | -5.33% | About once every 52 trading sessions24 comparable moves / 1,257 observations | +1.38% | -2.98% | -6.06% |
| 27 Jan 2025 | -3.27σ | -6.28% | About once every 140 trading sessions9 comparable moves / 1,257 observations | +0.03% | +8.03% | -5.48% |
| 6 Jan 2025 | +2.55σ | +5.07% | About once every 39 trading sessions32 comparable moves / 1,258 observations | -0.14% | +8.25% | +12.65% |
| 15 Oct 2024 | -6.09σ | -14.70% | Not previously observed in 5 years0 comparable moves / 1,258 observations | -3.55% | -5.87% | -10.77% |
| 3 Sep 2024 | -3.01σ | -9.52% | About once every 74 trading sessions17 comparable moves / 1,258 observations | +0.50% | -1.10% | -4.55% |
| 17 Jul 2024 | -5.29σ | -9.85% | Not previously observed in 5 years0 comparable moves / 1,258 observations | +0.68% | +0.72% | +2.88% |
| 17 Apr 2024 | -2.68σ | -4.95% | About once every 43 trading sessions29 comparable moves / 1,258 observations | -2.24% | +7.17% | +16.87% |
| 26 Jan 2024 | -3.32σ | -6.60% | About once every 126 trading sessions10 comparable moves / 1,258 observations | +0.12% | +0.38% | +14.35% |
| 18 Jan 2024 | +2.92σ | +4.89% | About once every 63 trading sessions20 comparable moves / 1,257 observations | +3.90% | +1.71% | +21.62% |
| 11 Dec 2023 | +2.76σ | +4.64% | About once every 50 trading sessions25 comparable moves / 1,258 observations | +0.33% | +0.73% | +14.75% |
| 10 Nov 2023 | +3.11σ | +5.50% | About once every 97 trading sessions13 comparable moves / 1,257 observations | -1.12% | +3.08% | +10.69% |
| 15 Sep 2023 | -3.10σ | -5.35% | About once every 97 trading sessions13 comparable moves / 1,257 observations | +0.50% | -1.99% | +0.82% |
| 25 May 2023 | +2.76σ | +6.20% | About once every 48 trading sessions26 comparable moves / 1,258 observations | +6.20% | +6.16% | +5.81% |
| 27 Apr 2023 | +3.45σ | +7.63% | About once every 126 trading sessions10 comparable moves / 1,258 observations | +0.49% | -0.29% | +21.06% |
| 27 Jan 2023 | -3.14σ | -6.85% | About once every 97 trading sessions13 comparable moves / 1,258 observations | -2.93% | +4.37% | -8.65% |
| 6 Jan 2023 | +2.66σ | +6.46% | About once every 48 trading sessions26 comparable moves / 1,258 observations | +2.70% | +4.39% | -4.84% |
| 10 Nov 2022 | +3.24σ | +9.10% | About once every 105 trading sessions12 comparable moves / 1,258 observations | +3.25% | +1.05% | +2.48% |
| 9 Aug 2022 | -2.95σ | -7.57% | About once every 64 trading sessions19 comparable moves / 1,219 observations | +4.52% | +6.61% | -9.90% |
| 18 Jan 2022 | -2.84σ | -7.20% | About once every 49 trading sessions22 comparable moves / 1,079 observations | -4.79% | -12.39% | -16.20% |
| 21 Dec 2021 | +2.77σ | +6.20% | About once every 42 trading sessions25 comparable moves / 1,061 observations | +0.93% | +5.06% | -8.72% |
| 29 Oct 2021 | +2.56σ | +4.90% | About once every 33 trading sessions31 comparable moves / 1,025 observations | +2.01% | +11.90% | +7.24% |
| 28 Oct 2021 | +2.66σ | +4.34% | About once every 39 trading sessions26 comparable moves / 1,024 observations | +4.90% | +16.18% | +15.58% |
| 28 Sep 2021 | -2.81σ | -5.13% | About once every 44 trading sessions23 comparable moves / 1,002 observations | -3.38% | -4.88% | +20.19% |
| 30 Jul 2021 | +4.15σ | +8.99% | 4 times in 4 years4 comparable moves / 961 observations | -0.65% | -1.77% | +2.14% |
| 10 May 2021 | -2.70σ | -6.19% | About once every 39 trading sessions23 comparable moves / 904 observations | +0.13% | +1.35% | +2.91% |
| 11 Feb 2021 | +3.09σ | +9.03% | About once every 56 trading sessions15 comparable moves / 844 observations | +2.26% | -1.76% | -1.40% |
| 27 Jan 2021 | -3.20σ | -6.30% | About once every 69 trading sessions12 comparable moves / 833 observations | +2.34% | +1.26% | +4.19% |
| 14 Jan 2021 | +2.50σ | +4.75% | About once every 28 trading sessions29 comparable moves / 825 observations | +0.08% | -0.11% | +7.28% |
| 7 Jan 2021 | +2.93σ | +4.89% | About once every 48 trading sessions17 comparable moves / 820 observations | +1.79% | +12.90% | +13.65% |
| 29 Oct 2020 | +2.62σ | +5.98% | About once every 39 trading sessions20 comparable moves / 773 observations | -2.36% | +15.04% | +27.57% |
The number has a method behind it
Sigma measures the size of a log return relative to volatility estimated before the period. Rarity is counted from actual historical standardized moves, not inferred from a normal distribution.
σt = ln(Ct / Ct−1) / vtvt ← t−1, t−2, …
Volatility adapts to the market regime with EWMA (λ = 0.94 for daily and weekly observations). Current-period returns are excluded. Each historical σ uses its own prior volatility.
Both directions count toward rarity. Reference history spans up to five years. A period with no prior exceedances is labelled unprecedented in the observed sample; it is never given an invented recurrence interval.
Stock observations use split-adjusted price returns, without dividend reinvestment. Commodities are explicitly labelled ETF price proxies; they do not represent spot commodity prices.
Questions behind the sigma
What does a 3σ move mean?
The period log return is three times the volatility estimated from earlier periods. Sigma is signed: negative for declines and positive for rises.
Why not calculate rarity from a normal distribution?
Market returns have heavy tails and changing volatility. We count actual past absolute sigma exceedances for the same instrument and period.
Does “once every 200 days” predict the next event?
No. It is the number of historical observed periods divided by comparable moves. Events can cluster and the market regime can change.
How much history is required?
At least three years of valid standardized observations, after a one-year volatility warm-up. This normally requires approximately four years of source history.
Are all instruments directly comparable?
The engine is shared, but each instrument has its own prices, calendar, volatility and reference sample. Commodity cards use explicitly labelled ETF proxies.
What happens on quiet days?
The page shows the largest covered standardized move, the complete rarity scale and recent records. Missing data is reported separately from market calm.
For information only. Historical observations are not investment advice and do not predict future moves. A rare move can be followed by another rare move.