Kalshi, Polymarket OI Drops 20% After World Cup Ends
Sports drove 80% of combined volume — now both platforms face a sharp post-tournament liquidity hangover.
Open interest on Kalshi and Polymarket dropped 20% as the FIFA World Cup concluded, with sports markets driving roughly 80% of combined platform volume throughout the tournament, according to The Block.
Why It Matters
The 20% open-interest decline illustrates how heavily prediction-market liquidity now depends on marquee sporting events rather than political or financial contracts — a structural concentration risk for platforms and liquidity providers alike. When a single event category accounts for 80% of volume, post-event drawdowns are predictable and sharp. For traders, thinner order books in the coming weeks mean wider spreads and reduced exit options on open positions. Platform revenue metrics will likely reflect the same contraction until the next high-profile event cycle begins.
Context
Kalshi and Polymarket have each expanded aggressively into sports prediction markets over the past two years, treating regulated and crypto-native audiences respectively as parallel growth channels. As of July 2026, both platforms compete directly for sports-event volume that previously flowed almost exclusively to traditional sportsbooks. The World Cup, held every four years, represents one of the largest single-event liquidity catalysts in global betting markets.
What's Next
Traders and analysts will watch whether open interest recovers toward pre-tournament baselines before the next major sports calendar milestone — likely NFL preseason or European club football — or whether platforms shed casual participants who signed up specifically for World Cup markets. Kalshi and Polymarket will need sustained non-sports volume, particularly in political and economic contracts, to smooth out these post-event troughs.
Gambling and prediction-market trading involve risk; open positions can lose value rapidly in low-liquidity conditions.
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