Prediction market activity on Kalshi and Polymarket contracted sharply after the 2026 FIFA World Cup final, with daily sports volumes plunging by as much as 70%. The drop confirms how reliant these platforms remain on major event cycles for high-frequency trading.
Combined open interest (OI) across the two platforms fell about 20% from a peak of roughly $2 billion in early July. On a smoothed weekly basis, total OI climbed from $1.2 billion in late May to nearly $1.8 billion in the week ending July 5, before receding to around $1.5 billion by the week ending July 19.
Sports volumes mirrored this trajectory. Kalshi’s sports-related turnover peaked near $9 billion in the week ending July 5, then dropped to roughly $4 billion by July 19—a 55% decline. Polymarket’s sports volume fell even more steeply, from $2.3 billion to $740 million over the same period, a drop of close to 70%. Throughout the tournament, sports markets accounted for about 80% of total volume on both venues, underscoring how concentrated activity became around the World Cup calendar.
The sharp contraction followed Spain’s 1-0 victory over Argentina in the final on July 19. The group stage had provided a dense schedule of matches across 48 teams, generating a steady stream of daily markets. As the tournament moved into the knockout rounds, the number of matches shrank, the daily market count fell, and turnover naturally declined.
This pattern illustrates how quickly liquidity can aggregate around a single catalyst—and how quickly it can evaporate once the catalyst ends. Volume, which measures daily turnover, collapsed immediately as the match schedule thinned, while open interest, representing outstanding stakes, unwound more slowly as markets settled.
Data from Polymarket’s World Cup winner market, compiled by DeFiOasis, revealed that 194,000 unique addresses traded the market. About two-thirds of them lost money, with most gains and losses under $100. At the top end, 54 addresses profited more than $100,000 each—five of them cleared $1 million—while 43 addresses lost over $100,000. The distribution points to broad retail participation with small positions and concentrated outcomes among large traders.
Looking ahead, prediction market volumes are expected to stay subdued relative to June and July highs until the next major event cycle. That catalyst is likely to be the U.S. midterm elections in the fall, which historically draw significant flows but do not replicate the match-by-match turnover of a global sports event. The challenge for Kalshi and Polymarket remains converting event-driven traffic into durable, long-term activity.
