Prediction Markets Hit $68B in a Month as Sportsbook Stocks Sink
Key Takeaways
Sports and combo volume across major exchanges rose about 72% to $68.2 billion in 30 days.Kalshi grew 65% but its market share slipped as Polymarket U.S., DKeX and Novig gained.Flutter and Draftkings shares are down more than 70% from their 2025 peaks.
A $68 Billion Month
Combined notional volume in sports and combo contracts across the exchanges tracked by Aldrin Research rose from $39.74 billion to $68.18 billion between the 30 days to Aug. 30 and the 30 days to Sept. 29, InGame reported. The jump came as college and NFL football returned. Notional volume counts every contract at its full $1 payout value, the industry’s standard measure, so it overstates the money that actually changed hands.
Most of the growth came from combos, the parlay-style contracts that bundle several outcomes into one. Combo volume more than doubled, from $18.3 billion to $41.7 billion, and accounted for 82% of the added volume. Straight sports contracts grew 23%, to $26.5 billion.
Kalshi remains the dominant venue. Its sports and combo volume rose 65%, from $30.2 billion to $50 billion, but its market share fell from 76.1% to 73.4%. The loss was sharper in combos, where Kalshi’s share dropped from 93.5% to 83.9%, even though its own combo volume more than doubled to $35 billion.
The fastest growth came from smaller rivals:
Polymarket U.S.: volume rose 127% to $8.3 billion, and its share climbed from 9.2% to 12.2%. Its combo volume jumped from $357.1 million to $3.77 billion. DKeX, Draftkings’ own exchange: grew from $88.7 million to $1.9 billion, overtaking others to rank third in combos. Novig, the sports-only exchange that recently brought on actress and endorser Sydney Sweeney as an equity partner: grew 136%, lifting its share from 1.5% to 2%.
Polymarket’s international exchange lost volume over the same period, so across both its exchanges, Polymarket’s combined share slipped slightly, from 16.8% to 16.5%.
Sportsbook Stocks Drop
Sportsbook stocks paint a different industry picture. Flutter, which owns Fanduel, closed at $74.54 on Sept. 30, and Draftkings at $19, according to market data. On Tuesday, InGame reported both stocks at their lowest levels in years: since March 2020 for Flutter and April 2023 for Draftkings. Both are down more than 70% from their 2025 peaks.
Flutter’s latest drop followed Brazil’s ban on online betting, as the company said it has stopped operating in the country to comply with the change. If the ban lasts through year-end, it expects 2026 revenue to fall by about $70 million and adjusted EBITDA by about $20 million, according to its Sept. 28 statement. Domestically, low hold rates at the start of the football season have added to the pressure. Jefferies analysts estimated in a note to clients that Flutter’s online sportsbook gross gaming revenue in New York is on track to fall 39% through the first three weeks of September.
Draftkings CEO Jason Robins said in September that his company’s shares fall on good news for prediction markets, even though the company is building its own prediction-market business. The company has also faced scrutiny over its marketing, after separate investigations by The New York Times and ProPublica into how it targets bettors. Analysts at Citizens pointed to an Outlier survey in which 35% of respondents cited better prices as a reason to choose prediction markets over sportsbooks.
Kalshi, meanwhile, is in advanced talks to raise $1 billion at a $40 billion valuation, Reuters reported this week. That private valuation would exceed the combined market value of Flutter and Draftkings, which InGame put at about $12.9 billion and $9.8 billion at Tuesday’s lows.
