Prediction markets represented about 27% of US legal sports betting activity on the World Cup, according to H2 Gambling Capital.
Prediction markets represented an estimated 27% of US legal sports betting activity during the World Cup, up from roughly 9% at the start of 2026.
The H2 Gambling Capital estimate, cited by Bloomberg ahead of Spain’s victory yesterday (19 July), used public data from the tournament’s first month. It does not compare identical measures.
Prediction market volume counts trading activity, including positions resold before settlement, whereas sportsbook handle generally records only the amount first wagered.
Even with that qualification, Kalshi repeatedly broke its trading records during the tournament. Activity sometimes approached 10 times the levels seen earlier this year.
According to public data, Kalshi, Polymarket and Robinhood’s Rothera helped prediction markets top $50bn in monthly volume in June.
Kalshi posted $31bn in notional trading volume in June. Polymarket’s international operations, which have increasingly come under fire, set a new monthly record at $10.8bn.
Its regulated US platform recorded $3.5bn, while Rothera came in at $2bn.
Kalshi also attracted more daily US mobile app users than DraftKings or FanDuel during the competition. Earlier reports had already predicted losses for sportsbooks.
Polymarket grew across both its international exchange and newer US operation. However, Kalshi still recorded more than twice Polymarket’s World Cup volume.
Prediction exchanges list sports contracts under Commodity Futures Trading Commission (CFTC) oversight. That route has enabled access in states without legal online sports betting.
It also generally allows customers from age 18, whereas licensed US sportsbooks commonly set the minimum at 21.
Gambling versus trading debate rages
Several state regulators argue that sports contracts amount to gambling, while prediction platforms maintain they are federally regulated derivatives. Multuiple courts are therefore considering where federal authority ends and state gambling control begins.
The commercial pressure goes beyond user numbers. Prediction market exchanges let customers buy and sell positions instead of betting against one operator, and earn transaction fees rather than retaining losing stakes.
That structure can deliver tighter prices when liquidity grows. It creates a direct problem for sportsbook margins, especially among customers who compare odds carefully.
Sportsbooks have responded with prediction products of their own. Their brands, payment systems and existing customer databases provide broad distribution.
World Cup activity also arrived as DraftKings and Flutter shares weakened. Both were down more than 25% during 2026 by the final weekend.
Prediction markets were not the only factor, however. The decline also reflected concern over taxes and slower sportsbook growth.
Separate study finds exchanges offered lower margins
A Citizens JMP Securities review compared six operators across 104 World Cup matches. It measured implied vig on match results and over-under goals.
Polymarket recorded the lowest average implied vig at 2.70%. Kalshi followed at 4.71%, ahead of DraftKings at 4.97% and FanDuel at 5.07%. BetMGM averaged 5.64%, while Fanatics reached 6.14%.
Polymarket offered the best pricing in every match studied. Without Polymarket, Kalshi led in 57 games. DraftKings led in 38, FanDuel in seven, BetMGM in one and Fanatics in one.
The report marked the second consecutive major event where Kalshi beat DraftKings and FanDuel on pricing, after it also led during March Madness after trailing both during the 2025 NFL season.
JMP analysts Jordan Bender and Isabella Slavin tied the shift to higher volume, deeper market-maker participation and stronger competition between liquidity providers.
The analysts explained: “Casual bettors are generally less price sensitive and may instead prioritise product experience, brand, or access in their state.
“If these trends continue at the current pace, we would expect the pricing advantage to widen vs. the sportsbooks, attracting liquidity providers and sophisticated users, strengthening the ecosystem over time.”
The NFL season will provide the next major comparison.
