Prediction market open interest climbed to a record $1.48 billion in the week ended June 15, marking a second consecutive weekly high and underscoring rapid growth in the sector as sports-related contracts fueled trading activity. Weekly trading volume also reached $10.8 billion, another all-time high for the industry.
According to a16z crypto, open interest, which measures the value of outstanding contracts that remain active in the market, has increased roughly sixfold over the past year. The metric reflects capital that traders continue to keep at risk rather than contracts that have already been settled.
“The recent surge represents a roughly sixfold increase over the past year, highlighting how users are maintaining longer-term financial positions and how prediction markets are maturing into durable market infrastructure,” a16z wrote in a market update.
The record open interest was driven largely by leading platforms Kalshi and Polymarket, while smaller venues including Opinion, Limitless and Myriad accounted for a comparatively smaller share of activity.
Growth extended beyond open interest. Weekly notional volume reached a record $12.2 billion, while fees generated by prediction market platforms climbed to an all-time high of $76.8 million. Active users also hit a record 426,975 during the period.
Sports contracts emerged as the dominant driver of activity, generating $5.8 billion in notional volume, nearly half of total market trading. The category was the largest source of volume on both Kalshi and Polymarket.
The ongoing 2026 FIFA World Cup contributed significantly to the surge in participation, attracting new users and increasing activity. Some traders reportedly placed seven-figure wagers on individual matches, while one trader reportedly generated $9.24 million in profits in a single day.
Separate market data showed prediction markets recorded $10.8 billion in weekly trading volume in the week ended June 15, another all-time high for the industry.
The increase reflects a sharp acceleration from a year earlier, when a typical week on prediction markets generated around half a billion dollars in trading volume and even the busiest weeks remained below $1 billion.
Industry observers attributed the latest spike in activity to a combination of high-profile global events, including the SpaceX initial public offering, a U.S.-Iran peace deal, the NBA Finals, the Stanley Cup Finals and the opening stages of the FIFA World Cup.
The data suggest prediction markets are attracting a broader user base beyond traditional political forecasting, with traders increasingly participating in markets tied to sports, economics, culture and cryptocurrency-related events.