About $200 million in trades on Polymarket in the first half of the year have been flagged as potential insider trading

In the first half of the year, about $200 million in trades on prediction markets were flagged as potential insider trading, and the top 1% of winners reaped more than half of the profits.
(Background: Prediction markets are taking over gambling markets; the World Cup accounts for 27% of total U.S. sports betting volume, and grew 3x within a month.)
(Additional context: In Polymarket’s World Cup betting pool, more than 66% of addresses are at a loss, while a small number of people are raking in $2.2 million)

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• $200 million suspicious trade volume in the first half of the year
• Trading methods of linked wallets exposed
• How do prediction markets work?

As prediction markets such as Polymarket and Kalshi continue to expand, the practice of placing bets using non-public information or an information advantage is coming under increasing scrutiny. Bloomberg Businessweek analyzed around 34,000 potential insider trades that Polysights flagged between August 2025 and June 2026. These trades show characteristics such as newly created accounts, low-probability entry, large wagers, and higher transaction concentration.

$200 million suspicious trade volume in the first half of the year

Data shows that during the period from January 1, 2026 to June 30, 2026, the value of suspicious trades flagged on Polymarket was about $200 million. Markets related to geopolitics and war drove a significant surge in abnormal trading volume.

Profits from potential insider trading are highly concentrated: among the profitable wallets, the top 1% of accounts captured more than half of the total gains, and 57% of the related wallets were created less than 24 hours before the trades.

Trading methods of linked wallets exposed

Some traders are reducing the chances of being detected by using multiple linked wallets and splitting orders. Taking 38 linked addresses as an example, these accounts placed bets in 90 geopolitics markets related to Iran and Venezuela, achieving a win rate as high as 98%, with cumulative profits of $1.6 million, and they withdrew the funds through the same Coinbase top-up address.

How do prediction markets work?

Polymarket says it will continue to monitor insider trading and other illegal activity, and to date it has transferred nearly 100 wallets to law enforcement. Its competitor Kalshi has also strengthened screening of identity and employment information, and restricted people who may influence outcomes—such as political candidates and athletes—from participating in related markets.

The advantage of prediction markets is “equal information for everyone,” but the data shows that it is often the holders of first-hand information who truly drive trading volume.

When 57% of the profitable wallets are created only within 24 hours after the market opens, it means that the market’s “fair competition” ends earlier than people might think. For users, before placing bets on the World Cup, elections, or geopolitical conflicts next time, it may be worth first paying attention to these linked wallets with 98% win rates.