On August 17, 2026, VolRoc recorded 122,521 active prediction markets across Kalshi and Polymarket, holding $1.28B in combined open interest. Day over day, active markets fell 40.0% and open interest fell 18.3% (vs August 16, 2026). Politics & Elections was the largest domain by open interest (40%), ahead of Sports (27%); together they accounted for 67% of all open interest. Kalshi carried 90% of active markets and Polymarket 10%.
Deterministic · template v1 · 2026-08-17
As of 2026-08-17 · 00:00 UTC
Active Markets
122,521
00:00 UTC freeze
Open Interest
$1.28B
Kalshi OI + Polymarket liquidity
Markets Traded · 24h
14,297
with trading activity
Kalshi / Polymarket
90% / 10%
by active-market count
Domain Composition — 12 domains
Mixed / Multi-category
47,085
Sports
44,333
Other
17,356
Politics & Elections
6,282
Entertainment & Culture
2,654
Crypto & Digital Assets
1,344
Technology & AI
893
Economics & Inflation
845
Companies & Business
724
Monetary Policy
416
World & Geopolitics
310
Climate & Weather
203
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 = 122,521.
Largest Kalshi Series
Cross-category multi-markets
47,085
Sports — multi-game parlays
32,956
Midterm control
1,080
Music — artist streams
743
U.S. House races
612
Nextteamnba
507
Nflwins
332
Ncaafwins
250
Primary vote shares
248
NFL — next team moves
230
Flprimary
213
Midtermvoteturn
203
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 17, 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 17, 2026.” https://volroc.ai/prediction-markets/2026-08-17/
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