Combined trading volume across Kalshi and Polymarket dropped 14.5% in August to $45.33 billion, marking the first meaningful pullback after months of relentless growth in the prediction markets sector.
The decline follows a record-setting July that saw $50.59 billion in combined volume across the platforms. That peak had a very specific catalyst: the FIFA World Cup, which ran from June 11 to July 19 and turbocharged sports betting contracts across both platforms. With the World Cup over, the question is whether prediction markets can sustain their growth trajectory without the world’s biggest sporting event driving the bulk of their volume.
The World Cup effect, in reverse
July’s $50.59 billion represented a 7.8% jump from June’s revised figure of $46.95 billion. The World Cup ran through most of that period, generating a surge in sports-related contracts that inflated overall volume numbers. August’s pullback is essentially the hangover from that event-driven spike, as casual bettors who opened accounts to wager on World Cup matches drifted away once the tournament ended.
Sports contracts have accounted for over 88% of recent activity on Kalshi. That concentration makes the platform highly sensitive to the sports calendar. Kalshi maintained 85-90% of its comparable weekly volume heading into late August, while Polymarket’s offshore platform saw a steeper contraction. The divergence reflects the different user bases: Kalhi draws more from sports bettors, while Polymarket attracts a mix of macro and political speculators.
The numbers break down as follows. Kalshi recorded $37.17 billion in volume in August, down 7.3% from $40.1 billion in July. Polymarket and its U.S. platform saw a combined $8.16 billion, down 36.7% from $12.89 billion in July. The steeper drop on Polymarket’s offshore platform suggests that its user base was more reliant on World Cup-driven activity than Kalshi’s, and that many of those users were temporary visitors who have since moved on.
Polymarket’s monthly volume data from DeFi Rate shows the scale of the swing. August’s $2.98 billion in global Polymarket volume represented a 61.5% drop from the platform’s earlier months, though the cumulative year-to-date total still sits at $55.95 billion. Sports made up 28% of Polymarket’s volume, politics and government 5.8%, and finance/Fed markets just 1.7%. The low share for finance-related contracts is notable given the macro volatility driven by the Iran war, bond selloff, and rate hike expectations that dominated headlines in late August.
NFL steps up, but cannot fill the gap
NFL preseason markets generated $167.8 million across Kalshi, Polymarket Global, and Polymarket US in the week ending August 16. Kalshi handled approximately 79% of that activity. The NFL season officially kicks off in September, which should provide a significant volume boost. But football’s betting markets, while large, are unlikely to match the World Cup’s global reach and the sheer number of contracts it generated across dozens of countries and hundreds of matches.
Kalshi also posted a notable milestone despite the broader downturn. For the week ending August 30, the platform’s weekly contract volume exceeded $10 billion for the first time, hitting $10.17 billion. That weekly figure suggests the platform’s baseline demand is growing even if the monthly numbers look soft. The weekly milestone also indicates that Kalshi’s user base is expanding beyond World Cup-driven speculative activity into other market categories, including weather contracts, political events, and economic indicators.
The CFTC-regulated exchange has leaned heavily into sports as its primary volume driver, but it has also been building out political, economic, and weather contracts. The challenge is that sports contracts generate the highest volume per user, while other categories tend to attract smaller, more analytical positions. As the sports calendar quiets down, Kalshi’s ability to drive volume from non-sports markets will determine whether the August dip is a blip or the beginning of a correction.
Different platforms, different audiences
Kalshi, operating as a CFTC-regulated exchange in the US, has the advantage of regulatory legitimacy and institutional access. Polymarket Global, meanwhile, has attracted more interest in macro and esports markets, benefiting from its permissionless structure that allows it to list contracts faster than its regulated competitor. The regulatory difference also affects how each platform handles dispute resolution and contract settlement, which matters for users who are betting large amounts on geopolitical or economic outcomes.
The volume gap between the two platforms is widening. Kalshi contributed $37.7 billion in July, roughly 74.5% of the combined total across both platforms. In August, that share held roughly steady, but the absolute numbers shrank on both sides. The data suggests that Kalshi’s regulated status gives it more resilience during downturns, while Polymarket’s offshore operations are more volatile and more dependent on event-driven spikes in speculative interest.
The broader prediction markets industry is still growing rapidly on a year-over-year basis. August’s $45.33 billion was well above the $25.66 billion seen in May, before the World Cup-driven surge began. The year-to-date cumulative volume across both platforms is tracking well ahead of 2025 levels. But the August pullback serves as a reminder that prediction market volume is heavily event-dependent, and the absence of a major catalyst can produce sharp month-over-month declines that look worse than they are.
Looking ahead, the US presidential midterm elections in November 2026 and the NFL season should provide volume catalysts for the rest of the year. The question is whether prediction markets can build enough non-sports demand to smooth out the seasonal volatility that the August data exposed. For now, the industry remains in growth mode, but the World Cup hangover shows the limits of event-driven volume and the challenge of maintaining momentum between major global events.
discussion