What is a prediction market?

A prediction market is an online marketplace where participants buy and sell shares whose value depends on the outcome of a future event. For yes/no events, a YES share pays $1 if the event happens and $0 otherwise; the current price between $0 and $1 represents the market's aggregate estimate of the probability. For example, if 'Hantavirus pandemic in 2026?' YES shares trade at $0.09, the crowd's estimated probability is 9%. Major prediction markets include Polymarket (crypto-based, global) and Kalshi (regulated US derivatives exchange). They are often used by researchers as forecasting signals for events ranging from elections to disease outbreaks, since aggregating many traders' bets can produce calibrated probabilities. OutbreakWatch displays Polymarket and Kalshi data; we do not facilitate trading.