Kalshi and Polymarket's trading volume in August decreased by 14.5% month-on-month, marking the first decline in a year

According to The Block data panel, the combined trading volume of Kalshi, Polymarket, and Polymarket US in August fell by 14.5% month-on-month to $45.33 billion, marking the first monthly decline in a year. Among them, Kalshi's trading volume in August was $37.17 billion, down 7.3% from $40.1 billion in July; the combined trading volume of Polymarket and its US platform was $8.16 billion, down 36.7% from $12.89 billion in July.

The decline in August occurred after a surge in summer prediction market activity driven by the World Cup (June 11 to July 19), but the August trading volume was still significantly higher than May's $25.66 billion. Meanwhile, Kalshi and Polymarket are facing increasingly stringent scrutiny from state-level regulators in the US, particularly regarding sports-related contracts, with more than ten states taking enforcement actions or filing lawsuits against the two platforms. Last week, Connecticut sued Kalshi, seeking to prevent the platform from offering sports contracts.

Despite the escalating legal disputes with state regulators, Kalshi continues to expand its presence in the sports sector, recently signing an agreement with the United States Tennis Association to become the exclusive prediction market partner for the US Open. Additionally, earlier this week, Kalshi permanently banned former US Congressman George Santos, marking its first permanent ban, due to Santos violating rules by betting on whether he would attend the State of the Union address, resulting in a fine of over $71,000.