Geopolitical and NBA betting markets see spike in open interest on Polymarket despite decreasing active traders, volume

Prediction markets on Polymarket, especially those linked to recent global tensions and geopolitical conflict, have seen a notable spike in open interest (OI), with Iran-related markets leading the surge last week.

The market "US military action on Iran before July," which is set to resolve next week, has seen OI grow to $6.19 million at the time of writing from $249,000 two weeks ago. "Will the US officially declare war on Iran before July?" has also spiked to $3.04 million from $0 in OI over the same period. Additional markets focused on Ali Khamenei, Iran’s supreme leader, have posted an average 10x surge in OI over the past several days.

The trend underscores how real-world events are increasingly "gamed" and "financialized," with Polymarket playing a central role in enabling that behavior.

Meanwhile, one of the only other high-profile markets to experience an uptrend in its OI is the one centered on the NBA champion. This market had $670,000 in OI at the start of 2025 and was standing at over $7.5 million on Sunday, just before Game 7 of the NBA Finals, which concluded with the Oklahoma City Thunder being crowned champions.

Despite the surge in Iran-related markets, they still represent only a fraction of the total OI across the Polymarket platform, which currently exceeds $131 million. Platform-wide OI has hovered near the $100 million mark for over six months, well below its all-time high of over $510 million during the U.S. presidential election cycle — a 74% decrease.

Further, both monthly active traders  and  volume are under half of their ATH levels, while new market creation is down 23%. The platform's growing diversity of markets, reflected in the composition of OI, signals a shift from concentrated political wagering (e.g., U.S. elections) toward broader, more event-driven speculation.

This is an excerpt from  The Block's Data & Insights newsletter . Dig into the numbers making up the industry's most thought-provoking trends.