Thirty-day volume in sports and combination contracts hit $68.2 billion as football returned. Polymarket's U.S. arm and DraftKings grew fastest from smaller bases.
The return of football has supercharged trading on prediction-market exchanges, and nearly all of the growth is coming from one product: the combination contract.
Notional volume in sports and combo contracts across tracked exchanges reached $68.18 billion in the 30 days through Sept. 29, up about 72% from $39.74 billion in the 30 days through Aug. 30. Combination contracts, which bundle several outcomes into a single wager in the style of a sportsbook parlay, climbed to $41.7 billion from $18.3 billion.
That $23.4 billion increase accounts for about 82% of the total $28.4 billion in added volume.
Kalshi grows, but others grow faster
Kalshi remains dominant. Its sports and combo volume rose to $50 billion from $30.2 billion. But its share of the category slipped to 73.4% from 76.1%, and its share of combination contracts fell more sharply, to 83.9% from 93.5%.
The share is going to newer entrants. Polymarket's U.S. platform more than doubled its volume, up 127% to $8.3 billion, lifting its share to 12.2% from 9.2%. DraftKings' prediction exchange, DKeX, went from $88.7 million to $1.9 billion, a roughly 21-fold increase in a single month.
Reading the figures carefully
The volume numbers are calculated on a notional basis, counting each contract at its $1 face value. That method overstates the amount of money that actually changes hands, since a contract priced at 20 cents is counted as a dollar of volume. The figures cover sports and combos only and are not comparable with all-category totals published elsewhere.
Even with that caveat, the direction is clear. The parlay format, long the most profitable product for traditional sportsbooks, has become the fastest-growing product on federally regulated event-contract exchanges.
The regulatory backdrop
That growth arrives as the Commodity Futures Trading Commission examines how exchanges use promotional incentive programs to attract traders, and as rule proposals on event contracts sit under review at the White House's regulatory office. Kalshi's own volume incentive program runs until at least Oct. 13. No regulator has tied its review to combo volume, but the timing puts the product under a brighter light.
What to watch: Whether the CFTC issues formal action on incentive programs, and whether Kalshi's combo share stabilizes once its incentive program ends. A further drop after Oct. 13 would suggest part of its lead was being bought rather than earned.