Polymarket’s Volume Fell 56% After the World Cup. Kalshi Held. New York City Is Probing the Ads.

Published August 12, 2026. Prediction market volume and market share data from Dune Analytics, The Block, and Sportico.

The World Cup ended on July 19. The volume data since then tells a clear story about which prediction market platform was built for the event and which was built for everything else.

Polymarket's combined weekly trading volume across its international and US exchanges fell 56% from June's record high, according to user-compiled data on Dune Analytics cited by Bloomberg today. Kalshi's drop over the same period was 25%.

What the July Numbers Show

July was a record month in aggregate. Combined volume across Kalshi, Polymarket international, and Polymarket US reached $50.59 billion — up 7.8% from June's $46.95 billion, according to The Block.

But the composition of that record matters. Kalshi posted $37.7 billion in July volume, up 14% from June. Polymarket's international exchange fell 26% to $7.9 billion — its presence propped up by Polymarket US, which launched its regulated American exchange in May and posted $5 billion in July, a 54% increase from June.

Strip out the World Cup and the gap becomes structural. Sports contracts accounted for roughly 80% of both platforms' volume during the tournament. Post-tournament, that share has fallen to approximately 60% on Kalshi and 50% on Polymarket. The difference in volume performance reflects the difference in product breadth: Kalshi currently lists 28,996 active markets. Polymarket lists 8,040.

Polymarket's daily fee revenue dropped approximately 40.5% after the tournament ended. Kalshi's fell 9.3%.

Track live prediction market prices across Kalshi and Polymarket at predictions.io/lobby/crypto.

What Made the World Cup Different

The scale of the event is worth recording. Combined volume in July across all platforms reached a record $50.59 billion — the highest monthly figure in the industry's history. A total of 194,000 wallet addresses traded Polymarket's World Cup winner market alone. Sports contracts accounted for roughly 80% of both platforms' total volume during the tournament, driven almost entirely by the World Cup.

Both platforms treated the tournament as a customer acquisition exercise. Kalshi ran a Times Square billboard featuring Lionel Messi, bought pitch-side signage at the World Cup final, and aired a national television campaign with Timothée Chalamet. Polymarket ran 45 ads during live World Cup broadcasts on Fox and Telemundo. The rest of the US prediction market industry combined ran 22.

The advertising investment was in the hundreds of millions of dollars. The hangover is the cost of building a business on a tournament that runs once every four years.

New York City Is Now Investigating

This morning, Bloomberg reported that New York City Council Speaker Julie Menin sent a formal list of questions to Polymarket, Kalshi, Coinbase, and Gemini Space Station's prediction market platform Titan as part of a legislative inquiry. The probe is examining whether existing city laws adequately protect residents from false or deceptive marketing by the platforms.

The NYC inquiry is part of a wider pattern. State officials in New York, Illinois, and Wisconsin have opened regulatory fronts against prediction markets since the start of the year, compounding a federal legal fight between platforms and state attorneys general over whether CFTC regulation preempts state gaming statutes.

What Comes Next

Polymarket US expects to launch custom parlays this month — a product that inflates the notional volume metric and should narrow the gap with Kalshi in headline numbers. Kalshi is rolling out perpetual futures. Both platforms are now running national TV advertising against a backdrop of midterm election markets heating up through November.

The 2026 midterm elections are the next major event-driven catalyst. Political markets drove the industry's initial breakout in 2024 and were responsible for the volume that preceded the World Cup surge. If the midterms produce close races and high-attention outcomes — which Kalshi and Polymarket traders are already pricing in — the summer lull may prove short.

Track live US politics prediction market prices across Kalshi and Polymarket at predictions.io/lobby/us-politics.

Short Version

Polymarket weekly volume down 56% from June's peak. Kalshi down 25%. July was still a record at $50.59B combined, but driven by World Cup. Post-tournament: Polymarket revenue -40.5%, Kalshi -9.3%. Kalshi has 28,996 markets vs Polymarket's 8,040. NYC Council now probing four platforms over advertising. Polymarket US launching parlays this month. Midterms are the next big catalyst. Live prices at predictions.io/lobby/crypto.

Track live prediction market prices across Kalshi and Polymarket at predictions.io/lobby/crypto.

Last updated: August 12, 2026. Sources: Bloomberg (August 12, 2026), The Block (August 3, 2026), Sportico, Dune Analytics, Odaily, KuCoin, Blockonomi.