Key takeaways Kalshi and Polymarket US smash monthly volume records Regulated US platforms dominate prediction market trading activity November elections could accelerate growth beyond sports
Kalshi and Polymarket US have broken their monthly trading volume records before October ends, highlighting how rapidly prediction markets are expanding in the United States ahead of November's midterm elections.
Kalshi generating approximately $65 billion in October trading volume, already 10% above its September record. Polymarket US reached $10 billion, exceeding its previous monthly total by roughly 15%.
Open interest also reached record levels in the reported snapshot, with Kalshi accounting for $2.05 billion and Polymarket US another $384 million.
Kalshi Captures 83% as Polymarket Shifts Toward US TradingKalshi controlled nearly 83% of combined trading volume across Kalshi, Polymarket US and Polymarket Global in The Block's comparison.
A year earlier, Kalshi's October volume stood at approximately $4.4 billion, roughly matching Polymarket's international platform. This October, Kalshi's reported volume was 18.7 times larger than Polymarket Global's.
Together, the two US-regulated exchanges generated 95.6% of activity across the three platforms.
Polymarket's expansion into the United States followed its $112 million acquisition of CFTC-licensed derivatives exchange QCEX.
Kalshi has meanwhile expanded its visibility through major sporting partnerships, including an agreement with the US Open.
The sports-driven expansion is also creating demand for comparison services. WagerBeasts, for example, aggregates sportsbook odds and market-based predictions, allowing users to compare prices across providers, including selected prediction-market venues.
Such services illustrate how a wider ecosystem is developing around sports forecasting, although odds comparisons are distinct from exchange trading volume.
Prediction Markets Gain Ground Against Crypto Spot TradingThe Block also reported that its prediction-market-to-spot-exchange volume ratio reached 11.42 in October, compared with 7.34 in September.
The indicator increased in ten of the previous twelve months, signaling stronger relative activity in prediction markets.
However, the figure is a dataset-specific ratio and should not be interpreted as evidence that prediction markets process 11.42 times as many dollars as cryptocurrency spot exchanges.
Robinhood's financial results provide another indication of the industry's commercial expansion.
Its prediction-market business generated $173 million in third-quarter revenue, compared with $120 million from cryptocurrency trading.
The company has also identified Bitcoin and gold contracts as expanding areas of demand, although sports remains its largest prediction category.
November Midterms Will Test Growth Beyond SportsThe November 3 US midterm elections represent an important opportunity to test whether political contracts can provide another major source of trading activity.
Sports markets have already helped prediction platforms attract broader audiences, but election-related demand may prove more concentrated around specific events.
Regulatory uncertainty remains another challenge. As our market comparison explains, federally regulated event contracts and traditional state-regulated sports betting can face different legal requirements.
Prediction markets are also reshaping brokerage economics. Robinhood previously generated 21% more revenue from event contracts than equity trading during the second quarter.
