Gamblers have placed nearly $9 million in bets on future measles cases in the US since January on platforms Kalshi and Polymarket. Researchers suggest these prediction markets offer accurate forecasts that could aid in modeling disease spread. The practice draws on the wisdom of crowds amid rising measles cases.
Prediction markets allow users to buy and sell shares on yes-or-no outcomes for future events, with share prices reflecting collective bets. A yes share costing 86 cents, for instance, pays $1 if correct, funded by losing bets. Since January, nearly $9 million has flowed into measles-related markets as cases rise across the US. Spencer J. Fox at Northern Arizona University noted that in June 2025, markets predicted around 2,000 cases by year-end; the actual tally reached 2,288. “I’ve seen many worse forecasts from our models,” Fox said. The concept traces back to 1988 University of Iowa economists forecasting elections, later expanded to diseases by researcher Philip Polgreen in 2003 for educational purposes. Commercial platforms like Kalshi and Polymarket, regulated by the Commodity Futures Trading Commission, now dominate but face criticism over bets on events like the wars in Iran and Ukraine, or the February 28, 2026, killing of Ayatollah Ali Khamenei—where trader Magamyman won $553,000. Fox sees potential in measles markets as an additional data stream for epidemiologists tracking vaccination rates, genomics, and climate. Yet he cautions they lack the granularity of scientific models and cannot replace expert forecasts for rare events. Cognitive scientist Emile Servan-Schreiber, CEO of Hypermind, attributes accuracy to crowd wisdom, where amateurs add cognitive diversity. Kalshi and Polymarket did not comment.
