On August 19, 2026, VolRoc recorded 189,870 active prediction markets across Kalshi and Polymarket, holding $1.55B in combined open interest. Day over day, active markets rose 31.4% and open interest rose 11.3% (vs August 18, 2026). Politics & Elections was the largest domain by open interest (36%), ahead of Sports (22%); together they accounted for 57% of all open interest. Kalshi carried 93% of active markets and Polymarket 7%.
Deterministic · template v1 · 2026-08-19
As of 2026-08-19 · 00:00 UTC
Active Markets
189,870
00:00 UTC freeze
Open Interest
$1.55B
Kalshi OI + Polymarket liquidity
Markets Traded · 24h
17,529
with trading activity
Kalshi / Polymarket
93% / 7%
by active-market count
Domain Composition — 12 domains
Mixed / Multi-category
141,255
Other
17,580
Sports
17,357
Politics & Elections
6,222
Entertainment & Culture
2,666
Crypto & Digital Assets
1,362
Technology & AI
893
Economics & Inflation
844
Companies & Business
693
Monetary Policy
416
World & Geopolitics
311
Climate & Weather
195
Science & Health
76
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 = 189,870.
Largest Kalshi Series
Cross-category multi-markets
141,255
Sports — multi-game parlays
3,686
Midterm control
1,102
Music — artist streams
771
U.S. House races
612
Nextteamnba
507
Mlbhr
343
Nflwins
341
Primary vote shares
312
Mlbhit
296
Mlbhrr
277
Ncaafwins
266
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 August 19, 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 — August 19, 2026.” https://volroc.ai/prediction-markets/2026-08-19/
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