TheBlock
Combined monthly trading volume at Kalshi, Polymarket and Polymarket US fell 14.5% in August to $45.33 billion, the first month-over-month decline in a year and a sharp reversal of the World Cup-driven summer spike, according to The Block's data dashboard.
Kalshi recorded $37.17 billion in August, down 7.3% from $40.1 billion in July. Polymarket and its U.S. platform together saw $8.16 billion, down 36.7% from $12.89 billion in July. The pullback followed a June 11 to July 19 FIFA World Cup window that pulled prediction-market activity to a multi-year high, and August's print, while down sharply, still sat well above May's $25.66 billion baseline.
Why it matters
The shape of the decline is more telling than the headline figure. Kalshi, the federally regulated exchange, gave back a modest 7.3% after a record run, while unregulated Polymarket lost more than a third of its monthly volume. That gap hints at where the demand is sticky versus event-driven, and tells investors which side of the regulated-versus-offshore split is currently carrying the category.
Layered on top of the volume drop is escalating state-level regulatory pressure. Over a dozen states have taken enforcement action or filed lawsuits against the two venues, with Connecticut last week suing Kalshi to block its sports-related contracts. The legal drag is heaviest in the sports vertical, which is also the vertical that powered most of the summer's gains.
Market impact
The August read is a clean reminder that prediction-market volume remains event-cyclical rather than steady-state. Even after the 15% pullback, the $45.3B combined monthly figure is still nearly double the May baseline, so the deceleration is a normalisation step off a peak rather than a category breakdown. What to watch next: whether September's NFL kickoff and the U.S. Open partnership Kalshi signed with the USTA can rebuild the sports-betting flow that the World Cup provided, and whether more state attorneys general follow Connecticut's litigation template against sports contracts.
Frequently asked questions
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How much did Kalshi and Polymarket volume fall in August?
Combined monthly volume at Kalshi, Polymarket and Polymarket US dropped 14.5% to $45.33 billion in August, the first month-over-month decline in a year, according to The Block's data dashboard.
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Why did prediction-market volume drop in August?
The pullback followed a FIFA World Cup spike between June 11 and July 19 that had pushed both venues to multi-year highs. The August print reflects normalisation off that event-driven peak rather than a category breakdown.
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How did Kalshi and Polymarket volume compare in August?
Kalshi recorded $37.17 billion, down 7.3% from $40.1 billion in July. Polymarket and Polymarket US together saw $8.16 billion, down 36.7% from $12.89 billion in July, a much sharper drop than Kalshi's.
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Are Kalshi and Polymarket facing regulatory action?
Over a dozen U.S. states have taken enforcement action or filed lawsuits against the two venues, focused on sports-related contracts. Connecticut sued Kalshi last week to block its sports contracts, escalating a months-long legal fight.
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What partnerships or product moves are the venues making now?
Kalshi signed an exclusive prediction-market partnership with the USTA to become the official partner of the U.S. Open, whose main draw began Aug. 30. The platform also issued its first-ever permanent ban, barring former U.S. Rep. George Santos and ordering him to pay over $71,000 in fines.
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