Kalshi Took More Than Three-Quarters of the Week
Kalshi registered around 77% of all the volume tracked from last week, with $15.8 billion. Polymarket came in a distant second with $3.6 billion. Nadex followed with $481.9 million and Rothera with $272.3 million, while Predict.fun and Opinion each cleared $120 million.
Polymarket had a decent weekend of its own, with $770.4 million on Saturday and $662.4 million on Sunday. However, Kalshi’s growth through September has been much faster and the gap between the two platforms is now the widest it has been all year.
American Football Pushed the Biggest Days to the Weekend
With September coming to a close, the sector’s trading volume over the course of the month has already broken past the previous highs set in July. These records have arrived just as the NFL and college football season in the US got underway. Most games are played over the weekend, hence why most of the sports trading is piling up during this period.
A large share of that flow runs through parlay-style combo contracts. A parlay bundles several outcomes into one bet. A trader might back three teams to win on the same Sunday afternoon, for example. The contract pays out only if every leg hits, so the odds are long and each contract often costs just a few cents.
That low price is where headline volume gets inflated. Kalshi counts every contract at its $1 payout value rather than what the trader paid. A $20 bet on a long-shot parlay priced at 5 cents buys 400 contracts, which shows up as $400 in volume. When thousands of those bets land on a busy football weekend, the dollar figures climb much faster than the money at risk.
The Fed, Crypto and the Midterms Added to the Total
Sports didn’t carry the whole week. The Federal Reserve’s September rate decision drew steady positioning on both Kalshi and Polymarket. Short-duration crypto markets, which ask whether Bitcoin or Ether will close above a set price within hours or by the end of the day, turned over repeatedly as prices moved.
Traders have also started positioning early for the Nov. 3 U.S. midterm elections, with control of both chambers of Congress at stake. Election contracts drove the last big volume cycle in 2024, and the midterms are now five weeks away. The NFL regular season runs into early January.
