+1 sessions
Median return -1.51%Completed observations: 23
- Middle 50%
- -3.92% … +0.29%
- Positive returns
- 30%
Moderna · Sigma Moves
Closed-period price moves, measured against their own history. One engine. Five markets. No forecasts.
Latest closed period
Moderna's latest move against its own history.
MRNA Rare
+8.83%
+2.70σ
About once every 36 trading sessions
35 comparable moves / 1,255 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 -4.51%Completed observations: 23
- Middle 50%
- -9.35% … -0.49%
- Positive returns
- 26%
+30 sessions
Median return -13.71%Completed observations: 23
- Middle 50%
- -24.74% … -3.46%
- Positive returns
- 22%
Every rare move, in context
Instrument: MRNA (price return)
| Date | σ | Move | Observed rarity | +1 sessions | +7 sessions | +30 sessions |
|---|---|---|---|---|---|---|
| 8 Jul 2025 | +2.70σ | +8.83% | About once every 36 trading sessions35 comparable moves / 1,255 observations | +0.77% | -1.04% | -14.23% |
| 6 May 2025 | -3.36σ | -12.25% | About once every 79 trading sessions16 comparable moves / 1,256 observations | -1.51% | -3.19% | +3.97% |
| 5 Mar 2025 | +3.15σ | +15.94% | About once every 63 trading sessions20 comparable moves / 1,256 observations | -2.58% | -1.68% | -28.46% |
| 13 Jan 2025 | -4.01σ | -16.80% | About once every 180 trading sessions7 comparable moves / 1,257 observations | -1.96% | +20.60% | -4.47% |
| 7 Jan 2025 | +3.33σ | +11.65% | About once every 74 trading sessions17 comparable moves / 1,258 observations | -9.17% | -28.34% | -25.25% |
| 11 Nov 2024 | -3.14σ | -8.71% | About once every 62 trading sessions20 comparable moves / 1,238 observations | +1.68% | -13.59% | -5.80% |
| 8 Nov 2024 | -2.97σ | -6.86% | About once every 54 trading sessions23 comparable moves / 1,237 observations | -8.71% | -20.37% | -15.46% |
| 12 Sep 2024 | -3.41σ | -12.36% | About once every 80 trading sessions15 comparable moves / 1,196 observations | -2.01% | -7.95% | -24.23% |
| 1 Aug 2024 | -9.07σ | -21.01% | Not previously observed in 5 years0 comparable moves / 1,167 observations | -8.06% | -13.68% | -27.49% |
| 26 Jun 2024 | -3.43σ | -11.01% | About once every 88 trading sessions13 comparable moves / 1,142 observations | -1.04% | -4.90% | -31.14% |
| 22 May 2024 | +3.66σ | +13.67% | About once every 112 trading sessions10 comparable moves / 1,119 observations | +0.42% | -9.50% | -28.70% |
| 2 May 2024 | +4.70σ | +12.68% | 3 times in 4 years3 comparable moves / 1,105 observations | -0.47% | +0.06% | +11.50% |
| 22 Feb 2024 | +3.80σ | +13.53% | About once every 211 trading sessions5 comparable moves / 1,056 observations | -3.00% | -3.46% | +3.46% |
| 2 Jan 2024 | +3.74σ | +13.12% | About once every 204 trading sessions5 comparable moves / 1,021 observations | -3.48% | -5.07% | -23.60% |
| 14 Dec 2023 | +3.22σ | +9.25% | About once every 84 trading sessions12 comparable moves / 1,010 observations | +0.16% | +13.35% | +19.33% |
| 16 Oct 2023 | -2.68σ | -6.47% | About once every 37 trading sessions26 comparable moves / 968 observations | -6.10% | -16.51% | -14.97% |
| 18 Sep 2023 | -3.48σ | -9.12% | About once every 119 trading sessions8 comparable moves / 948 observations | +2.50% | -4.51% | -28.87% |
| 21 Aug 2023 | +2.91σ | +9.31% | About once every 58 trading sessions16 comparable moves / 929 observations | +4.65% | +4.99% | -7.20% |
| 17 Aug 2023 | +2.91σ | +7.40% | About once every 62 trading sessions15 comparable moves / 927 observations | -4.35% | +7.14% | -2.78% |
| 7 Aug 2023 | -3.26σ | -6.46% | About once every 92 trading sessions10 comparable moves / 919 observations | -1.44% | -2.25% | +5.47% |
| 23 May 2023 | +3.74σ | +8.69% | About once every 174 trading sessions5 comparable moves / 868 observations | -4.47% | -5.26% | -13.71% |
| 17 Apr 2023 | -3.51σ | -8.36% | About once every 140 trading sessions6 comparable moves / 842 observations | -0.93% | -9.20% | -10.47% |
| 13 Dec 2022 | +5.35σ | +19.63% | 1 times in 3 years1 comparable moves / 758 observations | +5.78% | +5.47% | -4.15% |
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.