Prediction Market Open Interest Just Hit an All-Time High of $1.3 Billion as Lawmakers, Courts and Regulators Close In

Data from Artemis shows that open interest across all prediction markets hit new highs of $1.3 billion last month, up from $993.5 million in March. Kalshi is at the number one spot with $636.4 million while Polymarket is in close second at $589.8 million. The remaining platforms collectively hold less than $25 million. 

Kalshi posted a record $13.4 billion in spot volume in the month of April, up 12.6% from March, without a tentpole event like the Super Bowl driving activity. Polymarket’s April was a different story. Volume fell to $9.5 billion from $10.6 billion in the previous month. Despite this dip, open interest reaching new highs highlights that money entering these markets isn’t just passing through. 

Senate Bans, DOJ Indictments and State-Level Crackdowns

What makes this all time high all the more striking is that it arrived during a time where nearly every institutional player in the United States is closing in on the prediction market industry at the same time. 

Just days after the DOJ went after a U.S. Army Special Forces soldier for allegedly using classified information about the Maduro operation to place bets on Polymarket and reportedly walking away with around $410,000, the U.S. Senate voted unanimously to ban its own members from participating and trading on prediction markets. What were once theoretical regulatory concerns raised in comment letters have now become congressional votes and active enforcement cases. 

At the state level, we’re seeing an even more aggressive approach to these markets. A Nevada judge has already ordered Kalshi to start geofencing by today, May 4, blocking residents from accessing sports, election and entertainment contracts after calling the platform’s offerings “indistinguishable” from placing a bet at a licensed sportsbook. Minnesota legislators pushed forward a bill that would make it a felony to even host prediction markets in the state.

Most Traders Lose, A Tiny Group Wins and the Money Keeps Coming

Adding another layer to this, a Wall Street Journal analysis found that 67% of all Polymarket profits flow to just 0.1% of accounts, with fewer than 2,000 users capturing nearly $500 million. Bloomberg’s own review of every wallet active since early 2025 found over 100,000 accounts had lost at least $1,000, nearly double the number that posted comparable gains. 

None of this has slowed down the money. Kalshi’s valuation recently adjusted to $22 billion. Polymarket raised $600 million backed by Intercontinental Exchange, the company that owns the New York Stock Exchange. Hyperliquid has proposed adding prediction markets to its decentralized exchange. The CFTC just closed its public comment period on a rulemaking that will attempt to define the regulatory boundaries of the entire industry for the first time.

The $1.3 billion in open interest reflects a market growing faster than the legal system can figure out what to do with it. Whether that gap closes through regulation or the industry outrunning it entirely is the real bet being placed right now.