On October 8, 2026, VolRoc recorded 344,921 active prediction markets across Kalshi and Polymarket, holding $2.38B in combined open interest. Day over day, active markets rose 23.3% and open interest rose 14.4% (vs October 7, 2026). Politics & Elections was the largest domain by open interest (23%), ahead of Sports (17%); together they accounted for 40% of all open interest. Kalshi carried 92% of active markets and Polymarket 8%.
Deterministic · template v1 · 2026-10-08
As of 2026-10-08 · 00:00 UTC
Active Markets
344,921
00:00 UTC freeze
Open Interest
$2.38B
Kalshi OI + Polymarket liquidity
Markets Traded · 24h
22,216
with trading activity
Kalshi / Polymarket
92% / 8%
by active-market count
Domain Composition — 12 domains
Mixed / Multi-category
276,469
Other
27,037
Sports
24,155
Politics & Elections
8,575
Entertainment & Culture
2,936
Crypto & Digital Assets
1,409
Economics & Inflation
1,023
Companies & Business
868
Technology & AI
838
World & Geopolitics
698
Monetary Policy
510
Climate & Weather
322
Science & Health
81
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 = 344,921.
Largest Kalshi Series
Cross-category multi-markets
238,393
KXMVECROSSCATEGORY0
38,076
Midterm control
1,786
Votegeneral
1,526
U.S. House races
672
Music — artist streams
590
Ncaafspread
589
Midtermvoteturn
433
Nextteamnba
427
Nflwins
412
Ncaafwins
407
Ncaaftotal
347
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 October 8, 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 — October 8, 2026.” https://volroc.ai/prediction-markets/2026-10-08/
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