Prediction Market Volume Reaches $188 Billion as Kalshi Outpaces Polymarket

Prediction markets generated a record $188 billion in total volume between July and September, marking a nearly 70% quarter-over-quarter surge driven primarily by regulated venue Kalshi. According to tracking data from CryptoRank, aggregate trading volume expanded 21 times compared to Q3 2025 as demand for event-based contracts escalated rapidly. ## Notional Volume vs. Actual Cash Invested While headline trading volume reached $188 billion, data methodology documented by the Pew Research Center shows that prediction market metrics reflect contract full payout totals rather than cash paid. Each contract is measured at its full $1 notional value regardless of trading price, meaning a contract bought for 20 cents adds $1 to total reported volume. Figures from DeFi Rate show that Kalshi traders spent approximately $41 billion in cash to purchase $142 billion worth of contracts during the third quarter, working out to an average price of roughly 29 cents per dollar. Meanwhile, retail participants on competing platform Polymarket experienced widespread losses. An analysis by Galaxy Research covering 2.9 million human-operated retail accounts found that 69.2% finished below break-even, logging net cumulative losses of $338.9 million since 2020. ## Sports Contracts Drive Dominance and Regulatory Battles Kalshi, an exchange regulated by the Commodity Futures Trading Commission (CFTC), split trading volume evenly with Polymarket as recently as March before establishing a permanent weekly lead in mid-April, according to DefiLlama data. Sports event trading served as the primary growth engine for the platform: - Kalshi processed over $58 billion in sports trading volume in June and July alone. - Sports contracts represented 40% of Kalshi's Q3 trading volume and 68% of total buyer spending across prediction platforms over the past month. - Federal appeals courts remain divided over whether sports event contracts constitute illegal gambling. However, sports contracts have triggered severe state-level regulatory pushback. Officials in Ohio and Tennessee categorized sports contracts as gambling, and on September 25, a federal appeals court affirmed those states' authority to restrict Kalshi's local contract sales. That ruling directly contrasts with a separate federal appeals court decision in New Jersey that ruled in favor of Kalshi. Concurrently, Polymarket faces regulatory scrutiny, including a New York state lawsuit alleging illegal gambling operations. These legal disputes parallel broader market adjustments as authorities review exchange models, similar to recent CFTC retail trading frameworks designed for regulated leverage products. ## Why It Matters The explosive growth to $188 billion highlights a massive shift in trader interest toward event-based derivatives, though notional counting methods substantially inflate perceived liquidity compared to actual cash deployed. Furthermore, conflicting federal court decisions create significant legal uncertainty for CFTC-regulated derivative exchanges operating across state borders. The ultimate resolution of state gambling claims versus federal market oversight will determine whether prediction markets can maintain their growth trajectory in the United States.