Kalshi Claims 70% wash trading in Polymarket’s top markets

The volume war between Kalshi and Polymarket is spilling into public view. In the fresh rebuttal, executives are now openly disputing how big the market really is and what counts as “real” activity. This comes in when the prediction markets are facing constant scrutiny over multiple insider trading cases emerging on the platforms.

John Wang, Kalshi’s head of crypto, pushed back against claims that the two platforms did hit almost the same trading volumes in March. In a post, he said Kalshi processed $13 billion in March, while Polymarket handled closer to $10 billion. He tried to clear the air over disputing estimates that put both near $12 billion.

Kalshi Claims 70% wash trading in Polymarket’s top markets

Wang argued that comparisons often ignore structural differences between the platforms. He suggested that a fair comparison would separate Polymarket US volume as it’s largely sports-focused. Kalshi’s head of crypto put the steelman Spencer’s take in the middle and called it Poly Panama.

In an X post, he mentioned that even within Polymarket’s core markets, there are further adjustments needed. Wang pointed out that war-related contracts make up a huge share of Polymarket’s political volume. However, this is a category that Kalshi does not offer. If this section is kept apart, then it materially changes the comparison.

Wang also raised concerns about data quality. He claims that wash trading accounts for as much as 70% of activity in some of Polymarket’s top markets. Meanwhile, this figure is difficult to verify.

Another Kalshi-affiliated came in to support the claim. He stated that publicly shared figures were “not even sort of accurate. However, he cited Dune dashboard data showing Polymarket at roughly $9.5 billion in March volume. This number is quite low compared to Kalshi’s $13 billion.

Kalshi and Polymarket were nearly tied on total volume in March at ~$12B each. Strip out sports and it’s a different picture.

Polymarket did $7.5B in non-sports volume. Kalshi did $1.6B.

It’s weird that they’re even in the same category given very different positioning for… pic.twitter.com/XR0nHgoYE1

— Spencer Bogart (@CremeDeLaCrypto) April 26, 2026

As of April 2026, Kalshi has jumped over Polymarket in total trading volume. The platform had established itself as the market leader with around $37.5 billion in year-to-date notional volume. Meanwhile, Polymarket stood at around $29.2 billion. 

The debate comes in when prediction markets are rapidly scaling into a multi-billion-dollar sector. On the other hand, they are also facing high regulatory and legal pressure.

Prediction markets face heat over insider trading cases 

The most high-profile case emerged this week. US prosecutors have reportedly charged Gannon Ken Van Dyke with using classified intelligence to place bets on Polymarket. The bets were linked to the capture of Nicolás Maduro. Authorities allege the trades generated more than $400,000 in profit.

Around the same time, Kalshi disclosed that it had fined and suspended three congressional candidates for betting on their own election outcomes. This raises similar concerns about insider access to information.

Regulators are also beginning to take a harder stance globally. In Brazil, the Banco Central do Brasil has moved to block prediction markets entirely. It cited risks to investor protection and market integrity. The restrictions apply to contracts linked to events such as politics, sports, and social outcomes.

The US is witnessing a surge in criticism that is becoming more direct. Donald Trump said he was “not happy” with prediction markets. He described them as “somewhat of a casino.” However, these platforms continue to frame their products as financial instruments rather than bets.

That distinction is now being tested. A complaint in Wisconsin targeting firms including Kalshi and Polymarket argues that their own marketing materials resemble gambling services more than regulated financial products.

Despite the scrutiny, both platforms are continuing to expand. Kalshi says its crypto-related markets have grown rapidly in recent months, with volumes increasing nearly 10x, while Polymarket remains dominant in global, on-chain event trading.

The CFTC seems to be moving ahead from attempting to ban certain event contracts to actively asserting its “exclusive jurisdiction”. On March 12, 2026, the agency began a formal process to build a framework for prediction markets. It sought public input on whether event contracts should be classified as “swaps” or “futures”.

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