On June 18, 2026, VolRoc recorded 120,537 active prediction markets across Kalshi and Polymarket, holding $2.04B in combined open interest. Day over day, active markets fell 17.7% and open interest fell 2.2% (vs June 17, 2026). Sports was the largest domain by open interest (49%), ahead of Politics & Elections (19%); together they accounted for 69% of all open interest. Kalshi carried 93% of active markets and Polymarket 7%.
Deterministic · template v1 · 2026-06-18
As of 2026-06-18 · 00:00 UTC
Active Markets
120,537
00:00 UTC freeze
Open Interest
$2.04B
Kalshi OI + Polymarket liquidity
Markets Traded · 24h
15,844
with trading activity
Kalshi / Polymarket
93% / 7%
by active-market count
Domain Composition — 12 domains
Sports
80,395
Mixed / Multi-category
16,760
Other
12,516
Politics & Elections
5,572
Entertainment & Culture
2,189
Crypto & Digital Assets
1,057
Economics & Inflation
697
Companies & Business
430
Technology & AI
312
Monetary Policy
295
World & Geopolitics
160
Climate & Weather
84
Science & Health
70
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 = 120,537.
Largest Kalshi Series
Sports — multi-game parlays
67,936
Cross-category multi-markets
16,760
Music — artist streams
823
Midterm control
741
U.S. House races
607
Wcstageofelim
283
Wctotal
273
Nextteamnba
267
NFL — next team moves
253
California primaries
233
Wcteamtotal
211
Wcteamleadgoal
200
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 June 18, 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 — June 18, 2026.” https://volroc.ai/prediction-markets/2026-06-18/
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