Polymarket Has the Volume Gap to Close-Can It Catch Kalshi Before the $20B Week Turns Into a Trend?

Kalshi Kept Its Lead Even During a $20B Volume Surge

U.S. prediction markets put up a little over $20 billion in notional volume in about 12 days in July, but the market-share order hardly changed. Kalshi stayed first, and Polymarket remained second even as World Cup marketing drove a sudden burst of activity. In other words, the category had a volume spike, but Kalshi still looks like the market leader.

The Week-Over-Week Gap Is Still Sizeable

In the most recent full calendar week, Kalshi posted $5.2 billion in notional volume to Polymarket's $1.7 billion. The open-interest split is even starker: Kalshi held $788.2 million, or 59%, while Polymarket held $496.1 million, or 37%. That suggests Kalshi is capturing not just more trading activity, but also more of the capital that remains in positions between trades.

Why the Gap Matters for Polymarket

This is less a broad long-term verdict than a near-term positioning problem. Kalshi's regulatory edge and U.S. focus may be helping it hold the lead, while Polymarket still has to close the volume and liquidity gap. If this unusually busy week becomes a lasting pattern rather than a short-lived spike, Polymarket's path to catching Kalshi gets harder, not easier.