Open interest on prediction markets declined in July once the World Cup ended, though the two largest venues split the remaining flow unevenly.
Kalshi's share of total open interest slipped from roughly 62% to 59%, while Polymarket's grew from 27% to 41%, largely as capital left smaller platforms. The World Cup had concentrated more event-driven volume on Kalshi, so its post-tournament unwind was sharper. Even after the slip, Kalshi remains the clear market leader, though its lead over Polymarket has narrowed meaningfully in a single month.
Source: [source](http://telegraph.controller.bot/files/8336652911/AgACAgIAAxkBAAJFgWpu9nDay_bGjmYJOGwoJtHbVn1GAAITGWsbx494S7n64f1enyaPAQADAgADeQADPQQ)
Frequently asked questions
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Which prediction market platform leads in open interest?
Kalshi leads with roughly 59% of total open interest as of July, down from about 62% the month prior.
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How did Polymarket's market share change after the World Cup?
Polymarket's share grew from roughly 27% to 41% in July, largely because capital rotated out of smaller platforms rather than out of Kalshi.
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Why did Kalshi's share fall more than Polymarket's?
World Cup event-driven volume was more concentrated on Kalshi, so its post-tournament unwind was sharper than Polymarket's.
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Did prediction-market open interest rise or fall in July?
Total open interest declined in July as the World Cup ended, though Kalshi and Polymarket both held their positions as the top two venues.
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What is the gap between Kalshi and Polymarket now?
The gap has narrowed significantly: Kalshi leads by roughly 18 percentage points (59% vs 41%), down from a wider margin before the World Cup ended.
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