Woofun AI data shows that combined open interest for Kalshi and Polymarket decreased by 20% from an early July peak of approximately $2 billion to $1.5 billion in the week of July 19. Weekly smoothed figures indicate a rise from $1.2 billion at the end of May to $1.8 billion in the week of July 5 before the subsequent decline.

Trading volume experienced sharper contractions, with Kalshi’s sports volume dropping 55% from $9 billion to $4 billion, and Polymarket’s falling nearly 70% from $2.3 billion to $740 million. Sports trading previously accounted for roughly 80% of total volume on both platforms. Following Spain’s 1-0 victory over Argentina in the World Cup final, DeFiOasis statistics reveal that approximately 194,000 addresses participated in Polymarket’s champion market, with about two-thirds incurring losses. While 54 addresses gained over $100,000, including five exceeding $1 million, 43 addresses lost more than $100,000. Prediction market activity is expected to remain subdued until the U.S. midterm elections in the fall.