Kalshi’s market share slips to 79% as rivals gain ground

Stifel flags possible early saturation as Kalshi & Polymarket keep spending heavily on user growth.

The hit

Prediction markets pulled in more than $82bn in trading volume in September, according to Stifel, but growth lagged traditional sportsbooks on a comparable measure. On that handle-like measure, regulated prediction markets grew 27% month over month versus a 43% rise in regulated sportsbook handle, despite heavy spending by Kalshi & Polymarket on user acquisition.

Why it matters

Stifel says the slower growth could point to early market saturation & customer turnover, even as operators pour cash into prediction-market expansion. The firm warns that investment could weigh on near-term earnings. DraftKings could pull some of that spending into 2026, & Fanatics has indicated it could nearly triple marketing spend next year.

The record

Total prediction-market volume	$82bn in September
Regulated prediction-market volume	$76.7bn, up 64% month over month
Kalshi’s share of regulated volume	down to 79% from 86% in August
Taker-only volume across CFTC-regulated exchanges	$17.7bn, a stricter measure that strips out inflated notional volume, where parlay contracts bought for pennies can count as $1
US sportsbook handle growth	up 4% year over year across 13 states (Stifel)

What happens next

Watch third-quarter earnings from major sportsbook operators in the coming weeks for clarity on how prediction-market competition is hitting handle & profitability.

Sources: Prediction Markets Trail Sportsbooks In Key Growth Metric, Stifel Finds

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