Kalshi and Polymarket's combined volume falls 15% in August, first monthly decline in a year

Kalshi and Polymarket saw their combined volume decline last month, the first month-over-month drop in a year, following a World Cup-driven surge.

According to The Block's data dashboard, the combined monthly volume at Kalshi, Polymarket and Polymarket US fell 14.5% in August to $45.33 billion, marking the first decline since August 2025.

Specifically, Kalshi recorded $37.17 billion in volume in August, down 7.3% from $40.1 billion in July, while Polymarket and its U.S. platform saw a combined $8.16 billion, down 36.7% from $12.89 billion in July.

The August pullback followed a summer spike in prediction market activity driven by the World Cup, which ran from June 11 to July 19. Still, the August volume remained well above May's $25.66 billion.

Polymarket, Polymarket US and Kalshi Monthly Volume (The Block)