On August 13, 2026, VolRoc recorded 164,627 active prediction markets across Kalshi and Polymarket, holding $1.41B in combined open interest. Day over day, active markets fell 21.4% and open interest fell 7.7% (vs August 12, 2026). Politics & Elections was the largest domain by open interest (36%), ahead of Sports (33%); together they accounted for 68% of all open interest. Kalshi carried 92% of active markets and Polymarket 8%.
Deterministic · template v1 · 2026-08-13
As of 2026-08-13 · 00:00 UTC
Active Markets
164,627
00:00 UTC freeze
Open Interest
$1.41B
Kalshi OI + Polymarket liquidity
Markets Traded · 24h
17,161
with trading activity
Kalshi / Polymarket
92% / 8%
by active-market count
Domain Composition — 12 domains
Sports
75,191
Mixed / Multi-category
58,352
Other
17,326
Politics & Elections
6,218
Entertainment & Culture
2,683
Crypto & Digital Assets
1,421
Technology & AI
893
Economics & Inflation
838
Companies & Business
741
Monetary Policy
404
World & Geopolitics
297
Climate & Weather
187
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 = 164,627.
Largest Kalshi Series
Sports — multi-game parlays
62,501
Cross-category multi-markets
58,352
Midterm control
1,063
Music — artist streams
738
U.S. House races
609
Nextteamnba
505
Nflwins
314
Nflspread
307
Nfltotal
278
Ncaafwins
233
NFL — next team moves
229
Mlbhr
209
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 13, 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 13, 2026.” https://volroc.ai/prediction-markets/2026-08-13/
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