On September 6, 2026, VolRoc recorded 294,791 active prediction markets across Kalshi and Polymarket, holding $1.95B in combined open interest. Day over day, active markets fell 2.2% and open interest fell 6.5% (vs September 5, 2026). Politics & Elections was the largest domain by open interest (30%), ahead of Sports (21%); together they accounted for 51% of all open interest. Kalshi carried 79% of active markets and Polymarket 21%.
Deterministic · template v1 · 2026-09-06
As of 2026-09-06 · 00:00 UTC
Active Markets
294,791
00:00 UTC freeze
Open Interest
$1.95B
Kalshi OI + Polymarket liquidity
Markets Traded · 24h
26,986
with trading activity
Kalshi / Polymarket
79% / 21%
by active-market count
Domain Composition — 12 domains
Mixed / Multi-category
171,145
Other
58,187
Sports
43,504
Politics & Elections
10,865
Entertainment & Culture
3,207
Crypto & Digital Assets
1,813
Technology & AI
1,363
Climate & Weather
1,309
Economics & Inflation
993
World & Geopolitics
904
Companies & Business
852
Monetary Policy
535
Science & Health
114
Venue-agnostic subject taxonomy from Kalshi series prefixes and
Polymarket title keywords. A residual Other bucket is reported honestly.
Yes-price across both venues, 10 buckets from 0 to 100. n = 294,791.
Largest Kalshi Series
Cross-category multi-markets
171,145
—
21,744
Midterm control
1,250
Ncaafspread
841
Music — artist streams
736
U.S. House races
638
Ncaaftotal
621
Nextteamnba
514
Ncaafwins
399
Nflwins
381
Mlbhrr
369
Nflspread
348
Kalshi market families (Polymarket is not series-structured).
About & Citation
This is the fixed-hour (00:00 UTC) state of every active market on
Kalshi and Polymarket for September 6, 2026. The live
Observatory
shows the current diurnal value; this record is immutable. Open interest combines Kalshi
open interest with Polymarket USD liquidity as comparable USD magnitudes. Sources: Kalshi, Polymarket.
How to cite
“VolRoc Prediction Market Archive — September 6, 2026.” https://volroc.ai/prediction-markets/2026-09-06/
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