Prediction markets crossed $20 billion in weekly trading volume for the first time, according to data from Artemis. The sector recorded $20.4 billion in volume last week, surpassing the previous week's $19.8 billion and marking the highest sustained activity since the FIFA World Cup in June and July.
Kalshi dominated the market, accounting for approximately 77% of weekly volume at $15.8 billion. Polymarket followed with $3.6 billion, while Nadex, Rothera, Predict.fun, and Opinion collectively captured the remainder. Daily records were also set over the weekend, with Saturday and Sunday each reaching $4 billion in total volume across all platforms.
What Drove the Surge
Three primary factors contributed to the volume spike. The NFL and college football seasons in the United States began in September, with most games played on weekends. Sports trading activity, particularly through parlay contracts that bundle multiple outcomes into single bets, concentrated volume during weekends when most games occur.
Additionally, traders positioned around the Federal Reserve's September rate decision on both major platforms. Short-duration cryptocurrency contracts—betting whether Bitcoin or Ether will close above specific prices within hours or by day's end—generated repeated trading as prices fluctuated.
Early positioning for the U.S. midterm elections on November 3 also contributed to activity. Control of both chambers of Congress is at stake, and election contracts have historically driven significant volume cycles.
Market Structure and Volume Mechanics
Kalshi's dominance widened significantly in September, with the gap between Kalshi and Polymarket now at its widest point all year. On individual days, Kalshi processed approximately $3 billion in volume on both Saturday and Sunday, while Polymarket handled $770.4 million and $662.4 million respectively.
Parlay-style contracts, which pay out only if every leg of the bet succeeds, drive substantial headline volume figures. These contracts are priced low—often a few cents each—allowing traders to control significant notional exposure with small capital commitments. Because platforms count volume at contract payout value rather than at trader cost, a $20 bet on a long-shot parlay can register as hundreds of dollars in reported volume.
