Prediction markets reached $188 billion in third-quarter trading

Prediction-market trading reached a record $188 billion in the July-through-September quarter, nearly 70% above the preceding quarter and 21 times the level of a year earlier. Kalshi accounted for most of the total and was the principal driver of the quarter’s growth.

The figure was compiled by CryptoRank, according to a Yahoo Finance analysis published Oct. 6. Kalshi and Polymarket had been roughly even in trading volume as recently as March, but Kalshi had held a weekly lead from mid-April, based on DeFiLlama data.

Sports represented about 40% of Kalshi’s third-quarter volume. That share applies to Kalshi, rather than to the prediction-market sector as a whole. Kalshi’s sports trading exceeded $58 billion across June and July, while DeFi Rate data put sports at 68% of buyer spending across platforms in the month it examined.

As covered in September, the start of the NFL season was already lifting prediction-market activity across major platforms.

The $188 billion headline is a notional-volume measure, not the amount customers paid or collectively earned. Each contract is counted at its full potential payout, so a contract bought for 20 cents contributes $1 to reported volume. In the quarter examined, Kalshi buyers paid about $41 billion for $142 billion in contracts, or roughly 29 cents for each dollar of contract value.

That accounting distinction means volume totals using different methods can be difficult to compare, and neither trading volume nor open interest represents platform revenue. CryptoRank’s dashboard separately showed about $1.4 billion of combined open interest on Kalshi and Polymarket, a measure of outstanding positions rather than turnover over a period.

The expansion has moved prediction markets beyond elections into sports, political events, economic releases and Federal Reserve decisions. CryptoRank’s tracked contracts include congressional control, presidential nominations and Fed outcomes alongside sports markets.

The rapid rise in reported volume has also attracted scrutiny. CNBC found that nearly half the dollar volume in Kalshi ether perpetuals on Sept. 20 came from trades between $5,495 and $5,505, while observers identified unusual activity in some lower-probability Polymarket international contracts. Both companies denied wash trading or other inorganic activity. Andre Guettler said manufactured perpetual-futures volume could make headline growth overstate underlying trading demand.