Prediction markets captured an estimated 27% of US legal sports betting volume tied to the 2026 World Cup, up from roughly 9% at the start of the year, according to H2 Gambling Capital data reported by Bloomberg on July 19. Kalshi, Polymarket and Robinhood’s Rothera all posted record monthly volumes during the tournament, and the shift happened inside a single event.
Nine months ago, prediction platforms were a rounding error next to licensed sportsbooks. During the World Cup, they took roughly a quarter of the action. The open question is whether that share holds once the tournament fades, or whether it was a one-off driven by novelty and marketing spend.
Bloomberg flagged one caveat: the comparison is not exact. Prediction markets count trading activity, including positions traders buy and sell before an event finishes, while a sportsbook’s handle counts only the original bet. That is closer to comparing a stock exchange’s turnover with a casino’s drop, and traditional operators have not yet published their full tournament numbers. This is the kind of structural shift covered in TGE’s earlier feature on how prediction markets are reshaping US sports betting.
The Trillion-Dollar Trade: How Prediction Markets Are Reshaping US Sports Betting
Records fall fast
Kalshi posted $31 billion in notional trading volume in June alone, a figure that measures the total value of contracts traded rather than money kept by the platform. It broke its own records repeatedly through the tournament, at points trading at nearly 10 times the level it saw earlier in the year. It doubled the peak it had set during the New York Knicks’ playoff run weeks before.
Polymarket’s international exchange hit a new monthly high of $10.8 billion, while its separate, US-regulated platform recorded $3.5 billion. Rothera, the joint venture between Robinhood and Susquehanna International Group, posted $2 billion in its first full month live.
Even so, Kalshi traded more than twice Polymarket’s World Cup volume, and it drew more daily US mobile app users than DraftKings or FanDuel during the competition.
One reason platforms like Kalshi can move this fast is regulatory. They operate under Commodity Futures Trading Commission (CFTC) oversight as financial derivatives, not under state gambling licences, which lets them offer sports contracts in states that do not allow legal online sports betting. They also generally accept customers from age 18, against the 21 minimum most licensed sportsbooks require.
Several state regulators reject that framing. A judge in Michigan has temporarily barred Kalshi’s sports contracts, and Nevada regulators have pursued a contempt motion over geofencing. The platforms maintain they are federally regulated derivatives, and that argument is now playing out in multiple courtrooms at once. European regulators have taken a similar line, with Spain blocking Kalshi and Polymarket in a licensing crackdown.
Price beats marketing
Volume explains how fast prediction markets are growing. A separate Citizens JMP Securities study explains why bettors might prefer them. Analysts reviewed six operators across the tournament’s 104 matches and measured implied vig, the built-in margin a platform bakes into its odds, on match results and over-under goals.
Polymarket posted the lowest average vig at 2.70%, meaning bettors gave up less of their potential winnings to the house. Kalshi followed at 4.71%, ahead of DraftKings at 4.97% and FanDuel at 5.07%. BetMGM and Fanatics trailed at 5.64% and 6.14%.
Polymarket offered the best price in every match studied. Strip Polymarket out, and Kalshi still led on price in 57 games, ahead of DraftKings’ 38. This is the second straight major event where Kalshi has beaten the two biggest US sportsbooks on price, having also led during March Madness after trailing both throughout the 2025 NFL season.
JMP analysts Jordan Bender and Isabella Slavin wrote:
Casual bettors are generally less price sensitive and may instead prioritise product experience, brand, or access in their state.
That line frames how the industry should read the story. Sharper traders will keep chasing the best price, and prediction markets are increasingly winning that fight. Casual bettors, who make up most of a sportsbook’s customer base, tend to stick with the app they already trust rather than shop for the tightest margin.
Eyes on the NFL
DraftKings and Flutter shares were both down more than 25% year-to-date by the tournament’s final weekend. Fortune reported that tax concerns and slower sportsbook growth were also weighing on the stocks, so prediction markets are one pressure among several rather than the sole cause of the decline.
Sportsbooks have started building their own prediction-style products, betting that their existing brands, payment systems and customer databases can offset a pricing disadvantage.
The deeper threat is structural. An exchange like Kalshi or Polymarket lets customers trade positions against each other and earns a fee on the transaction, rather than taking the other side of every bet and profiting when customers lose. That setup can produce tighter pricing as more traders join, the trend JMP’s analysts expect to continue. Kalshi is separately weighing a public listing after its annualised revenue reportedly tripled to $2 billion.
The pricing gap comes weeks after lawmakers in Ohio moved to tax prediction markets under the same framework as licensed sportsbooks, and after Kalshi’s World Cup partnership with ADI Predictstreet. The NFL season, with a far larger betting base than the World Cup, will show whether Kalshi’s pricing edge is a World Cup anomaly or the start of a lasting shift in where US bettors put their money.
Source: H2 Gambling Capital, Citizens JMP Securities
