Prediction markets recorded their best month ever in October, with aggregate trading volume across the sector clearing the $100 billion threshold for the first time. These platforms let traders buy and sell contracts pegged to the outcomes of real-world events — election results, sports games, crypto price moves — with each contract settling at $1 if the event occurs and $0 if it does not. Data from Artemis shows total monthly volume reached $123.3 billion, representing growth of approximately 53.9% over the previous all-time high set in September. The number of trades also set a fresh record, reaching 642.9 million for the month.

Kalshi Drove the Bulk of Record Activity

Market share data shows Kalshi accounted for most of the record month. The platform drew $98.2 billion in trading volume over the course of the month — roughly 80% of the entire sector — and processed 465.5 million trades. Polymarket came in a distant second with $20.2 billion in volume and 148 million trades.

The remaining, smaller platforms held only a tiny slice of the market, although Nadex crossed the $2 billion monthly volume mark and Rothera saw volumes exceed $1 billion for a second consecutive month.

Football Season Fueled Three Straight Weekly Records

The NFL and college football seasons were a massive catalyst for the record month, with sports by far the largest trading category in October. Kalshi set three back-to-back weekly trading volume records during the month, the largest of which came in the week ending October 25, when the platform drew more than $25 billion in volume over seven days.

A large share of that money moved through combos, Kalshi's parlay product. Ticker Tracker data shows that, across the full month, combos took a 67.6% share of Kalshi's volume. Most of those bets were long shots priced below 1 cent.

This detail adds an important nuance when interpreting the headline volume figure. Kalshi records each contract at its full $1 payout value, regardless of how much the trader paid to enter the position. A parlay bought for less than a cent can therefore still add a full dollar to the total. This is where the platform's simultaneous record in trader count growth becomes significant, because it provides a second perspective confirming that growth is genuinely ramping up.

Midterm and Bitcoin Markets Added to the October Total

The upcoming U.S. midterm elections on November 3 also drew an influx of capital into political markets. Midterm markets passed $1.4 billion in volume for the month, and Kalshi alone accounted for nearly $1.1 billion of that total. As of October 31, Kalshi's House control market had traded about $170 million, while its Senate market stood near $111 million.

Crypto-based contracts grew as well. Crypto volume on Kalshi and Polymarket crossed $3 billion for the first time in October, and did so in consecutive weeks. Kalshi's 15-minute Bitcoin up/down contract was the standout, letting traders wager on whether BTC finishes higher or lower within a quarter of an hour — a cadence far shorter than the season-long football markets or the midterm contracts that stay open until Election Day.

Polymarket's US Arm Hit Its Own Monthly High

Polymarket's regulated U.S. platform set a new monthly high of nearly $10 billion in October, about 15% above its previous record. Combos grew to more than 20% of the platform's volume within days of their wider rollout, suggesting Polymarket is now running the same parlay-heavy playbook that carried Kalshi through football season.

Money also flowed into global event markets on the platform, including contracts tied to Brazil's presidential election and the Federal Reserve's October rate decision.

Midterm contracts are set to settle after Tuesday's vote, while the football markets that drove most of October's volume still have the rest of the regular season ahead.