Polymarket’s prediction-market share falls to 17.2% as Kalshi holds lead

Polymarket’s international exchange and Polymarket US accounted for 17.2% of face-value prediction-market trading in the 30 days before Oct. 29, a small decline from 18% in August and a far steeper retreat from its once dominant position.

Polymarket held 93.8% of the market in October 2024, before the presidential election and before Polymarket US existed. Its share fell to 73.2% the following month, then to 24.3% in July. Although Kalshi overtook Polymarket in September 2025, the two venues were roughly level as recently as March 2026.

The figures measure contracts at their $1 payout value rather than the price traders paid. That convention can substantially enlarge reported activity in low-cost contracts, including parlays. Gaming America reported that Polymarket’s share rose to 20.1% when measured by cash paid, while Kalshi’s fell from 75.8% on a face-value basis to 71.7% on that measure.

DeFi Rate’s latest 30-day tracker, covering Oct. 3 through Nov. 1, recorded $126.5 billion in face-value contracts across nine venues. Kalshi handled 75% of that total, while the tracker displayed rounded shares of 12% for Polymarket US and 4% for Polymarket International. Traders paid $30 billion in cash over the same period.

Sports have been central to the shift. Pew Research Center found that sports trading drove most of the rise in combined Kalshi and Polymarket volume from $26 billion in May to $53 billion in July. In June and July, Kalshi recorded more than $58 billion in sports trading, while Polymarket approached $22 billion.

The tracker also put spending on sports single markets at $15.3 billion. Crypto accounted for 25% of spending on those single markets and finance for 3%; the category figures exclude parlays. The tracker recorded $7.5 billion paid on combination contracts over 30 days, a category that can be especially sensitive to the difference between face-value volume and cash staked.

Polymarket remains ahead in U.S. search interest, a separate measure from trading. It held 54.6% of U.S. search demand in September, compared with 28.9% for Kalshi and 11.9% for Novig, although Polymarket’s share had fallen from 79.6% in May. Its daily search share recovered to 64% on Oct. 28.

Polymarket US, which is regulated by the Commodity Futures Trading Commission, has sought to rebuild share through trader incentives. It filed nine submissions with the regulator between Oct. 2 and Oct. 26 amending seven deposit, rebate and referral programmes. Its revised deposit-and-trading programme runs from Nov. 9 through May 9, 2027, and offers eligible individual traders up to $2,000 in non-withdrawable credits.

Kalshi also certified a taker-fee rebate programme on Oct. 27. It returns 15% to 50% of taker fees to qualifying self-clearing members and excludes combination contracts.