Sports and crypto drove prediction market record as politics lagged

Four platforms recorded their highest single-month nominal volume in September, reaching $75.5 billion, and the US midterm elections had almost nothing to do with it.

Political contracts generated $901 million across the period. That figure sounds substantial until you place it against the total: politics accounted for roughly one dollar in every eighty-three traded. The record was built on NFL kickoffs, college football weekends, fifteen-minute cryptocurrency windows, and a contract structure called combos that most of the coverage has not yet properly explained.

Combos bundle several outcomes into a single position, similar to a sportsbook parlay. They trade for cents. A contract with a maximum one-dollar payout contributes one dollar to nominal volume regardless of what the buyer actually paid. When Kalshi generated $34.2 billion in September nominal volume from combos alone, that number does not mean thirty-four billion dollars changed hands. It means a very large quantity of cheap positions each added their face value to the headline figure. Kalshi's average purchase price per dollar of contract fell from thirty-two cents in July to twenty-four cents by September. The industry's record month is partly a record in arithmetic.

This matters for anyone pricing the prediction market sector's legal exposure. The state attorneys general suing Kalshi and Novig are suing over sports event contracts. The federal argument turns on whether those contracts are swaps regulated by the Commodity Exchange Act or gambling subject to state law. What September's volume data shows is that the economic activity generating the litigation risk is not political forecasting — it is sports and crypto, running on a continuous calendar of events that never waits for an election cycle.

The consensus read has treated prediction markets as an election-infrastructure story, a quadrennial phenomenon that matters during campaign season and quiets between cycles. The September data undermines that frame. Sports provide a weekly settlement rhythm; short-duration crypto contracts let traders redeploy after each position closes rather than wait months for a resolution. The industry has built a volume engine that runs independently of the political calendar the press keeps watching.

Polymarket handled more than half of September's political trading across the four platforms, which makes it the dominant venue for the use case most people associate with prediction markets. Kalshi's dominance came from somewhere else entirely. Its share of total nominal volume rose from sixty-nine percent in July to seventy-three percent by September — driven by combos and crypto, not by any particular electoral question.

The legal proceedings currently occupying every prediction market desk are framed around gambling law. The volume data says the industry being argued over in those courtrooms is primarily a sports and crypto trading business that happens to also offer election contracts. That gap between the legal narrative and the commercial reality is where the mispricing lives.