On September 14, 2026, VolRoc recorded 286,681 active prediction markets across Kalshi and Polymarket, holding $1.74B in combined open interest. Day over day, active markets fell 21.7% and open interest fell 15.2% (vs September 13, 2026). Politics & Elections was the largest domain by open interest (33%), ahead of Sports (20%); together they accounted for 53% of all open interest. Kalshi carried 82% of active markets and Polymarket 18%.
Deterministic · template v1 · 2026-09-14
As of 2026-09-14 · 00:00 UTC
Active Markets
286,681
00:00 UTC freeze
Open Interest
$1.74B
Kalshi OI + Polymarket liquidity
Markets Traded · 24h
23,639
with trading activity
Kalshi / Polymarket
82% / 18%
by active-market count
Domain Composition — 12 domains
Mixed / Multi-category
198,119
Sports
34,427
Other
33,853
Politics & Elections
10,550
Entertainment & Culture
3,135
Crypto & Digital Assets
1,711
Technology & AI
1,394
Economics & Inflation
875
World & Geopolitics
873
Companies & Business
780
Monetary Policy
553
Climate & Weather
296
Science & Health
115
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 = 286,681.
Largest Kalshi Series
Cross-category multi-markets
161,489
KXMVECROSSCATEGORY0
36,630
Midterm control
1,340
Votegeneral
1,140
Music — artist streams
711
U.S. House races
647
Nextteamnba
454
Ncaafwins
424
Nflwins
403
Midtermvoteturn
277
Nflffleadertop
239
Ncaafgame
235
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 14, 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 14, 2026.” https://volroc.ai/prediction-markets/2026-09-14/
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