+1 sessions
Median return -0.52%Completed observations: 28
- Middle 50%
- -1.41% … +0.54%
- Positive returns
- 32%
Pfizer · Sigma Moves
Closed-period price moves, measured against their own history. One engine. Five markets. No forecasts.
Latest closed period
Pfizer's latest move against its own history.
PFE Rare
+4.26%
+2.97σ
About once every 60 trading sessions
21 comparable moves / 1,259 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 -0.33%Completed observations: 28
- Middle 50%
- -2.00% … +2.70%
- Positive returns
- 43%
+30 sessions
Median return -1.60%Completed observations: 28
- Middle 50%
- -8.64% … +6.05%
- Positive returns
- 43%
Every rare move, in context
Instrument: PFE (price return)
| Date | σ | Move | Observed rarity | +1 sessions | +7 sessions | +30 sessions |
|---|---|---|---|---|---|---|
| 6 Mar 2024 | +2.97σ | +4.26% | About once every 60 trading sessions21 comparable moves / 1,259 observations | -1.47% | +2.76% | -6.62% |
| 13 Dec 2023 | -4.26σ | -6.72% | About once every 210 trading sessions6 comparable moves / 1,258 observations | -1.99% | +6.53% | +3.08% |
| 1 Dec 2023 | -3.45σ | -5.12% | About once every 105 trading sessions12 comparable moves / 1,257 observations | +1.28% | -1.14% | -2.63% |
| 18 Oct 2023 | -2.68σ | -4.09% | About once every 43 trading sessions29 comparable moves / 1,257 observations | -0.70% | -4.14% | -2.99% |
| 16 Oct 2023 | +2.67σ | +3.61% | About once every 43 trading sessions29 comparable moves / 1,257 observations | -1.56% | -7.63% | -10.76% |
| 29 Sep 2023 | +2.89σ | +3.37% | About once every 55 trading sessions23 comparable moves / 1,257 observations | +2.32% | +0.00% | -11.12% |
| 6 Sep 2023 | -2.61σ | -2.85% | About once every 36 trading sessions35 comparable moves / 1,257 observations | -0.26% | -0.87% | -8.61% |
| 17 Aug 2023 | +2.54σ | +2.90% | About once every 33 trading sessions38 comparable moves / 1,257 observations | +0.41% | -0.82% | -9.15% |
| 26 Jun 2023 | -2.60σ | -3.68% | About once every 35 trading sessions36 comparable moves / 1,257 observations | -1.27% | -3.42% | -3.39% |
| 22 May 2023 | +5.82σ | +5.38% | 1 times in 5 years1 comparable moves / 1,258 observations | +2.30% | -1.88% | -8.05% |
| 9 Jan 2023 | -3.30σ | -4.97% | About once every 79 trading sessions16 comparable moves / 1,258 observations | -1.59% | -7.09% | -12.42% |
| 16 Dec 2022 | -2.65σ | -4.12% | About once every 37 trading sessions34 comparable moves / 1,258 observations | -0.08% | -1.17% | -14.46% |
| 21 Oct 2022 | +3.32σ | +4.75% | About once every 84 trading sessions15 comparable moves / 1,258 observations | +1.31% | +6.81% | +12.86% |
| 11 Aug 2022 | -2.66σ | -3.32% | About once every 38 trading sessions32 comparable moves / 1,221 observations | +3.77% | +1.26% | -8.72% |
| 26 Nov 2021 | +2.65σ | +6.11% | About once every 33 trading sessions32 comparable moves / 1,044 observations | -2.96% | -4.22% | +4.15% |
| 5 Nov 2021 | +6.98σ | +10.86% | 1 times in 4 years1 comparable moves / 1,030 observations | -0.58% | +2.04% | +25.53% |
| 2 Nov 2021 | +3.88σ | +4.15% | About once every 114 trading sessions9 comparable moves / 1,027 observations | -1.39% | +10.41% | +29.37% |
| 10 Aug 2021 | +3.16σ | +4.81% | About once every 65 trading sessions15 comparable moves / 968 observations | -3.90% | +1.27% | -8.80% |
| 3 Aug 2021 | +2.99σ | +3.91% | About once every 51 trading sessions19 comparable moves / 963 observations | -1.07% | +3.42% | -1.99% |
| 28 Jul 2021 | +3.57σ | +3.21% | About once every 87 trading sessions11 comparable moves / 959 observations | -1.52% | +3.73% | +5.94% |
| 20 Jul 2021 | +2.72σ | +2.24% | About once every 41 trading sessions23 comparable moves / 953 observations | -0.07% | +4.24% | +12.23% |
| 9 Jun 2021 | +2.90σ | +2.47% | About once every 49 trading sessions19 comparable moves / 925 observations | +2.19% | -2.51% | +4.17% |
| 3 May 2021 | +2.93σ | +3.05% | About once every 50 trading sessions18 comparable moves / 899 observations | +0.30% | -0.35% | -0.60% |
| 16 Apr 2021 | +2.69σ | +2.58% | About once every 39 trading sessions23 comparable moves / 888 observations | +0.93% | -0.31% | +0.41% |
| 3 Mar 2021 | +2.72σ | +2.63% | About once every 41 trading sessions21 comparable moves / 857 observations | -0.55% | +1.60% | +9.33% |
| 9 Nov 2020 | +4.12σ | +7.69% | About once every 111 trading sessions7 comparable moves / 780 observations | -1.33% | -2.34% | -1.21% |
| 28 Oct 2020 | -4.27σ | -5.29% | About once every 154 trading sessions5 comparable moves / 772 observations | -0.48% | +2.68% | +24.07% |
| 16 Oct 2020 | +3.80σ | +3.83% | About once every 96 trading sessions8 comparable moves / 764 observations | -0.40% | -1.37% | +6.40% |
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.