+1 sessions
Median return +0.62%Completed observations: 21
- Middle 50%
- -0.44% … +2.06%
- Positive returns
- 62%
Qualcomm · Sigma Moves
Closed-period price moves, measured against their own history. One engine. Five markets. No forecasts.
Latest closed period
Qualcomm's latest move against its own history.
QCOM Rare
-4.21%
-2.87σ
About once every 52 trading sessions
24 comparable moves / 1,257 observations
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 -0.28%Completed observations: 21
- Middle 50%
- -2.77% … +4.38%
- Positive returns
- 48%
+30 sessions
Median return +0.51%Completed observations: 21
- Middle 50%
- -5.50% … +7.55%
- Positive returns
- 52%
Every rare move, in context
Instrument: QCOM (price return)
| Date | σ | Move | Observed rarity | +1 sessions | +7 sessions | +30 sessions |
|---|---|---|---|---|---|---|
| 25 Oct 2023 | -2.87σ | -4.21% | About once every 52 trading sessions24 comparable moves / 1,257 observations | +0.80% | +14.07% | +26.88% |
| 7 Sep 2023 | -4.18σ | -7.22% | About once every 180 trading sessions7 comparable moves / 1,257 observations | -0.24% | +5.97% | +4.59% |
| 3 Aug 2023 | -4.49σ | -8.18% | About once every 251 trading sessions5 comparable moves / 1,257 observations | +2.36% | -3.94% | -4.68% |
| 26 May 2023 | +3.34σ | +6.09% | About once every 105 trading sessions12 comparable moves / 1,258 observations | +5.12% | +4.38% | +7.55% |
| 4 May 2023 | -3.58σ | -5.54% | About once every 140 trading sessions9 comparable moves / 1,258 observations | +2.06% | -0.28% | +15.11% |
| 10 Nov 2022 | +2.92σ | +9.28% | About once every 57 trading sessions22 comparable moves / 1,258 observations | +0.62% | -0.40% | -8.15% |
| 3 Nov 2022 | -3.09σ | -7.66% | About once every 66 trading sessions19 comparable moves / 1,258 observations | +2.71% | +16.29% | +10.25% |
| 13 Sep 2022 | -2.83σ | -6.07% | About once every 46 trading sessions27 comparable moves / 1,243 observations | +2.08% | -1.00% | -4.61% |
| 16 Jun 2022 | -2.90σ | -7.79% | About once every 49 trading sessions24 comparable moves / 1,183 observations | +0.14% | +8.92% | +22.02% |
| 28 Apr 2022 | +3.35σ | +9.69% | About once every 82 trading sessions14 comparable moves / 1,149 observations | -5.74% | -8.95% | -10.12% |
| 7 Mar 2022 | -2.55σ | -7.49% | About once every 33 trading sessions34 comparable moves / 1,112 observations | +0.44% | +0.23% | -6.03% |
| 18 Jan 2022 | -2.56σ | -5.21% | About once every 33 trading sessions33 comparable moves / 1,079 observations | -3.57% | -9.87% | -5.37% |
| 16 Nov 2021 | +2.51σ | +7.89% | About once every 31 trading sessions34 comparable moves / 1,037 observations | +0.95% | -3.34% | +0.51% |
| 4 Nov 2021 | +9.34σ | +12.73% | 1 times in 4 years1 comparable moves / 1,029 observations | +4.43% | +7.94% | +13.25% |
| 17 Sep 2021 | -2.98σ | -3.47% | About once every 52 trading sessions19 comparable moves / 995 observations | -0.63% | -2.77% | -0.42% |
| 29 Jul 2021 | +4.32σ | +6.00% | About once every 120 trading sessions8 comparable moves / 960 observations | -0.79% | -2.70% | -5.50% |
| 10 May 2021 | -3.20σ | -6.46% | About once every 70 trading sessions13 comparable moves / 904 observations | -0.44% | +1.33% | +4.76% |
| 4 Feb 2021 | -4.08σ | -8.83% | About once every 105 trading sessions8 comparable moves / 839 observations | -1.44% | -0.55% | -11.46% |
| 27 Jan 2021 | -2.82σ | -5.46% | About once every 42 trading sessions20 comparable moves / 833 observations | +1.22% | -5.10% | -14.27% |
| 11 Dec 2020 | -3.13σ | -7.36% | About once every 62 trading sessions13 comparable moves / 803 observations | +1.39% | +1.43% | +6.51% |
| 5 Nov 2020 | +5.67σ | +12.75% | 3 times in 3 years3 comparable moves / 778 observations | -0.28% | +2.52% | +1.38% |
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.