Prediction Market Platforms See August Trading Volume Decline 14.5%

Key Takeaways

Table of Contents

Combined trading volume across Kalshi and Polymarket decreased 14.5% in August, reaching $45.33 billion.
August represented the first monthly volume decrease since August 2025 for prediction market platforms.
Kalshi’s August volume reached $37.17 billion, representing a 7.3% decline from the previous month.
Combined Polymarket and Polymarket US activity fell 36.7%, totaling $8.16 billion.
Trading momentum from FIFA World Cup activity during June and July substantially decreased.

Major prediction market platforms experienced a significant volume contraction in August, breaking a consecutive streak of monthly expansion lasting an entire year. Trading activity across Kalshi, Polymarket, and Polymarket US decreased 14.5% to reach $45.33 billion, according to The Block’s data dashboard.

This contraction arrived after July established a record with $50.59 billion in aggregate volume. The FIFA World Cup, spanning from June 11 through July 19, had generated substantial interest in sports-related prediction contracts during those months.

August Trading Activity Contracts Across Platforms

Kalshi’s August trading reached $37.17 billion, showing a 7.3% reduction from July’s $40.1 billion. Meanwhile, Polymarket US and Polymarket collectively generated $8.16 billion, marking a substantial 36.7% reduction from the previous month’s $12.89 billion.

Despite the monthly contraction, August figures remained considerably higher than May’s $25.66 billion aggregate total. July had demonstrated a 7.8% increase compared to June’s adjusted $46.95 billion, illustrating the significant impact World Cup-related trading had on overall market performance.

FIFA World Cup Trading Momentum Subsides

Sports-related contracts have dominated recent platform activity on Kalshi, comprising more than 88% of total trading. Kalshi captured approximately 74.5% of the aggregate July volume among leading prediction market operators.

Polymarket’s offshore operations experienced a more pronounced downturn. Despite this, sports markets maintained considerable activity. NFL preseason contracts accumulated $167.8 million across Kalshi, Polymarket Global and Polymarket US during the week concluding August 16.

State-Level Legal Actions Intensify

Both Kalshi and Polymarket confront increasing legal challenges from state regulatory authorities concerning sports-related prediction contracts. More than twelve states have initiated enforcement proceedings or litigation against these platforms.

Connecticut sued Kalshi during the previous week seeking to prohibit sports contracts. This legal action amplifies an existing conflict between the state and the CFTC-regulated platform regarding jurisdictional authority over such offerings.

Kalshi Advances Sports Partnerships During Downturn

Despite reduced monthly volume figures, Kalshi pursued expansion within the sports sector. The platform recently finalized an arrangement with the U.S. Tennis Association, becoming the exclusive prediction market collaborator for the U.S. Open tournament.

Kalshi achieved a notable weekly benchmark approaching the conclusion of August. Trading volume surpassed $10 billion for the initial time during the week ending August 30, attaining $10.17 billion regardless of the overall monthly reduction.

The platform imposed a permanent trading ban on former U.S. Representative George Santos following his participation in a contract related to his State of the Union appearance. He received financial penalties exceeding $71,000.