Kalshi, Polymarket trading volume posts first monthly decline in a year

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Kalshi, Polymarket trading volume decline

Highlights

Combined monthly volume at Kalshi, Polymarket and Polymarket U.S. fell 14.5% in August to $45.33 billion, marking the first decline in a year.
Kalshi's August trading volume dropped 7.3% to $37.17 billion, while Polymarket and its U.S. platform plunged 36.7% to $8.16 billion compared to July.
Kalshi faces mounting state regulatory actions—including a recent Connecticut lawsuit—even as it expands in sports, striking an exclusive partnership with the U.S. Open starting August 30.

August volumes retreat after summer spike

The Block's data dashboard shows combined monthly volume at Kalshi, Polymarket and Polymarket U.S. falls 14.5% in August to $45.33 billion, the first monthly decline in a year.

Kalshi records $37.17 billion in August volume, down 7.3% from $40.1 billion in July. Polymarket and its U.S. platform post a combined $8.16 billion, down 36.7% from $12.89 billion a month earlier.

The August slowdown follows a jump in prediction market trading during the World Cup, which runs from June 11 to July 19. Even with the decline, August volume remains well above May's $25.66 billion.

Regulatory pressure grows as Kalshi expands in sports

Both Kalshi and Polymarket are facing increased scrutiny from state regulators in the U.S., particularly over sports-related contracts. More than a dozen states have taken enforcement action or filed lawsuits against the two platforms.

Connecticut sued Kalshi last week in an effort to block the platform from offering sports contracts, intensifying a legal dispute that has lasted for months. Despite those legal fights, Kalshi continues to broaden its sports presence and recently signed a deal with the U.S. Tennis Association to become the exclusive prediction market partner of the U.S. Open, whose main draw begins Aug. 30.

Earlier this week, Kalshi permanently banned former U.S. Rep. George Santos from trading on the platform in its first-ever permanent ban. The company says Santos broke its rules by trading on whether he would attend the State of the Union, and he was ordered to pay a fine of more than $71,000.

In our earlier coverage of prediction market pricing for the August U.S. jobs report, we noted that traders on Kalshi and Polymarket were positioning for a cautious rebound after July showed net job losses. Market odds were roughly even that payroll gains would top 50,000, with a wide spread of outcomes reflecting uncertainty after recent forecasting misses. The piece also explained how these contracts are tied to official Bureau of Labor Statistics data and why the upcoming release was a key focal point for traders.

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