Current probability
51¢
30-day movement
23.0 pts
Share of MIDVOL variance42%
MIDVOLBelief Volatility · 30-day
Midterms Uncertainty Index
MIDVOL is a forward-looking measure of uncertainty across the five possible balance-of-power outcomes for control of Congress. It combines the uncertainty visible in current prediction-market prices with a forecast of how much the full outcome map may move over the next 30 days. Higher uncertainty means prices are distributed across more plausible outcomes; lower uncertainty means they are concentrating around fewer. The measure is non-directional – it describes the magnitude of movement across the whole map, not which party will win.
Outcome uncertainty now
High uncertainty74%
Several materially different outcomes remain plausible. Prices imply the equivalent of 2.5 equally likely outcomes out of 5.
LowModerateHighVery high
Based only on current outcome prices, this reading changes when the odds change – not simply as election day approaches. Bands are fixed descriptive ranges, not historical percentiles.
Expected movement · next 30 days
35.5†probability points
The model’s 30-day forecast for combined repricing across all 5 outcomes.
The pre-de-vig price sum was below the overround tolerance. Series record ↓
What changed · recent readings
Expected movement fell
From changing odds
-0.430 pts
From the calendar
+0.057 pts
Observed Loading...Updates about every 5 minutes127 days to settlement
MIDVOL over time
Official history since August 6, 2026
Track the 30-day MIDVOL forecast or switch to current outcome uncertainty. The forecast view separates changes in prices from the effect of election day drawing closer.
30-day reading, past 24 hours
Loading history…
Published reading
No calendar-versus-beliefs split yet – the frozen-price path does not span enough of this window. It fills in as history accrues.
SOURCE: BELIEF SYSTEMS (2026)
Where uncertainty sits
MIDVOL covers the whole balance-of-power map. Outcomes stay in the same grid order so a price move never rewrites the visual story.
Current probability
1¢
30-day movement
4.5 pts
Share of MIDVOL variance2%
Current probability
36¢
30-day movement
22.2 pts
Share of MIDVOL variance39%
Current probability
11¢
30-day movement
14.6 pts
Share of MIDVOL variance17%
Current probability
0¢
30-day movement
2.3 pts
Share of MIDVOL variance0%
How to read MIDVOL
What it measures
Root-mean-square movement across the complete outcome distribution over the next 30 days.
What the points mean
The combined size of likely repricing across all outcomes – not a predicted move in one contract.
What it does not mean
It gives no political direction, is not annualized, and is not a confidence range for any single outcome.
Cite this reading
Belief Systems. Midterms Uncertainty Index (MIDVOL-30), Loading.... beliefsystems.xyz/volatility/midvol.
Series record
- Methodology
- fbv-v1.2
- Clock
- clock-v1.0
- Revision
- 0
- Publication
- published
- Sensitivity band
- 35.43 – 35.62 ptsthe headline recomputed at each gated leg's own bid and ask
- Disclosed checks (1)
- underround_flag – the pre-de-vig price sum was below the overround tolerance
Point-in-time snapshotas of 2026-08-18
ReadingsEvery published value with its gates, versions and counterfactualCSV · 26 KBOutcomesPer-outcome prices, budgets and horizon values, one row per readingCSV · 46 KBAttributionPer-outcome decomposition of every published moveCSV · 10 KB
Published rows are never restated. A correction is appended at the next revision, and the row as originally published stays in the archive unchanged – take the highest revision per timestamp. Join the three files on computation_id, not on the timestamp.
MIDVOL is a benchmark data product. It is not investable, not a recommendation, and not a forecast of any outcome.