Kalshi and Polymarket, monthly trading volume 'decreases' for the first time in a year... Is the World Cup effect over?

▲ Kalshi, Prediction Market, New York Stock Exchange/AI Generated Image

The trading volume of the prediction market, which had been rapidly expanding, mainly centered on Kalshi and Polymarket, has turned to a monthly decrease for the first time in a year.

According to The Crypto Basic on September 2 (local time), the combined trading volume of Kalshi, Polymarket, and Polymarket US platforms in August recorded $45.33 billion, a 14.5% decrease from the previous month. This is the first time the monthly trading volume has decreased since August 2025.

Kalshi's trading volume in August was tallied at $37.17 billion, a 7.3% decrease from $40.1 billion in July. The combined trading volume of Polymarket and its US platform plummeted by 36.7% from $12.89 billion to $8.16 billion.

The decrease in trading volume occurred immediately after the end of the World Cup. The World Cup, held from June 11 to July 19, was cited as a major factor that boosted prediction market trading during the summer. However, the combined trading volume in August remained 76.7% higher than the $25.66 billion recorded in May, before the World Cup.

Regulatory disputes continue in various US states. More than 12 states have pursued enforcement actions or lawsuits against Kalshi and Polymarket over sports event contracts. Connecticut filed a lawsuit last week to stop Kalshi from offering sports contracts. Despite regulatory conflicts, Kalshi expanded its business by signing a multi-year contract with the United States Tennis Association (USTA) to become the exclusive prediction market partner for the 2026 US Open.

Kalshi also strengthened its enforcement of trading regulations. The company permanently banned former US Representative George Santos from its platform. This is the first lifetime trading ban in Kalshi's history. Contract trading related to his attendance at the State of the Union address became an issue, and Kalshi also imposed a fine exceeding $71,000.

[Article Summary]

-The combined trading volume of Kalshi and Polymarket in August was $45.33 billion, a 14.5% decrease from the previous month.

-This is the first monthly decrease in trading volume since August 2025, and Polymarket's affiliated trading volume plummeted by 36.7% in one month.

-Despite the end of the World Cup and regulatory disputes in various US states, August's trading volume remained 76.7% higher than in May.

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