On September 2, 2026, VolRoc recorded 278,803 active prediction markets across Kalshi and Polymarket, holding $1.91B in combined open interest. Day over day, active markets rose 17.8% and open interest rose 4.8% (vs September 1, 2026). Politics & Elections was the largest domain by open interest (31%), ahead of Sports (20%); together they accounted for 51% of all open interest. Kalshi carried 79% of active markets and Polymarket 21%.
Deterministic · template v1 · 2026-09-02
As of 2026-09-02 · 00:00 UTC
Active Markets
278,803
00:00 UTC freeze
Open Interest
$1.91B
Kalshi OI + Polymarket liquidity
Markets Traded · 24h
26,911
with trading activity
Kalshi / Polymarket
79% / 21%
by active-market count
Domain Composition — 12 domains
Mixed / Multi-category
174,535
Other
42,331
Sports
40,584
Politics & Elections
10,687
Entertainment & Culture
2,757
Crypto & Digital Assets
1,890
Technology & AI
1,369
Climate & Weather
1,212
Economics & Inflation
995
Companies & Business
978
World & Geopolitics
825
Monetary Policy
529
Science & Health
111
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 = 278,803.
Largest Kalshi Series
Cross-category multi-markets
174,535
—
8,903
Midterm control
1,229
Ncaafspread
767
Music — artist streams
734
U.S. House races
635
Mlbhrr
528
Nextteamnba
513
Ncaaftotal
425
Nflwins
373
Ncaafwins
372
Ncaafgame
352
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 2, 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 2, 2026.” https://volroc.ai/prediction-markets/2026-09-02/
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