Open interest across prediction markets reached a record $2.8 billion last week, up from around $1.1 billion in August. The rise marks a sustained expansion in capital committed to event-based trading.
Why it matters
The growth puts prediction markets firmly on the radar of the broader derivatives and decentralized finance sectors. However, the market remains heavily concentrated rather than evenly distributed across platforms.
Kalshi accounts for roughly 71% of total open interest, while Polymarket holds about 24%. Together, the two venues represent roughly 95% of the market, leaving a narrow group of platforms driving the current expansion.
Market impact
The record suggests rising participation and liquidity in prediction markets, but the concentration creates a clear dependency on the leading venues. Future growth will be measured not only by total open interest, but also by whether activity spreads beyond Kalshi and Polymarket.
Source: [source](https://webappcsdfedsssd.controller.bot/media/files/8336652911/AgACAgIAAxkBAAJW3WrWLih7yzttB7DWzCOLqesDGQd5AALbH2sbMMmxSsa8QD-H0oWRAQADAgADeQADPQQ?sig=un_RWvgsFcRbycoSZE-48lcjRqg0UNnOOetQcj7Q99U)
Frequently asked questions
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How high did prediction-market open interest reach?
Open interest reached a new all-time high of $2.8 billion last week.
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How much has prediction-market open interest grown since August?
It rose from around $1.1 billion in August to $2.8 billion last week.
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Which platform holds the largest share of open interest?
Kalshi holds the largest share, accounting for roughly 71% of total open interest.
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What share of open interest does Polymarket hold?
Polymarket accounts for about 24% of total open interest.
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Why is market concentration important in prediction markets?
Kalshi and Polymarket together represent roughly 95% of open interest, so current growth is concentrated among two leading venues.
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