On August 29, 2026, VolRoc recorded 283,177 active prediction markets across Kalshi and Polymarket, holding $2.00B in combined open interest. Day over day, active markets rose 17.2% and open interest rose 10.5% (vs August 28, 2026). Politics & Elections was the largest domain by open interest (29%), ahead of Sports (22%); together they accounted for 51% of all open interest. Kalshi carried 79% of active markets and Polymarket 21%.
Deterministic · template v1 · 2026-08-29
As of 2026-08-29 · 00:00 UTC
Active Markets
283,177
00:00 UTC freeze
Open Interest
$2.00B
Kalshi OI + Polymarket liquidity
Markets Traded · 24h
27,056
with trading activity
Kalshi / Polymarket
79% / 21%
by active-market count
Domain Composition — 12 domains
Mixed / Multi-category
175,385
Other
46,537
Sports
38,796
Politics & Elections
10,622
Entertainment & Culture
3,253
Crypto & Digital Assets
1,886
Technology & AI
1,790
Climate & Weather
1,325
Companies & Business
1,034
Economics & Inflation
976
World & Geopolitics
901
Monetary Policy
532
Science & Health
140
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 = 283,177.
Largest Kalshi Series
Cross-category multi-markets
175,385
—
10,871
Midterm control
1,203
Music — artist streams
754
U.S. House races
625
Nflspread
545
Nextteamnba
512
Ncaafspread
510
Ncaafgame
371
Nflwins
363
Nfltotal
356
Ncaafwins
335
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 29, 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 29, 2026.” https://volroc.ai/prediction-markets/2026-08-29/
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