Low-odds trades on Polymarket’s international exchange draw scrutiny

Trading on Polymarket’s international exchange is drawing fresh scrutiny after lower-probability outcomes in several multi-contract markets attracted more volume than the favourites. The pattern has appeared in election, sports and central-bank contracts, prompting some industry observers to question whether reported activity has been inflated or reflects wash trading.

CNBC reported Sept. 30 that the anomaly was absent from September trading in 2028 presidential-nominee contracts on Polymarket’s CFTC-regulated U.S. exchange. The international venue is not overseen by U.S. regulators.

The disparity was particularly conspicuous in the platform’s 2026 FIFA World Cup market. Spain’s winning contract had traded about $152 million, while Egypt’s attracted roughly $158 million despite its probability never rising above 0.5%. Morocco’s contract drew slightly more volume than Spain’s although its probability never exceeded 2%.

In Polymarket’s market on Ethiopia’s prime minister, Abiy Ahmed had 98% odds and about $170,000 in volume after winning the election. Gedion Timothewos, whose odds remained below 3% for months, drew almost $56 million in trades.

Activity in that Ethiopian market rose more than 6.7-fold between June 21, when reports confirmed Ahmed’s victory, and Sept. 25. Its highest reported daily volume, more than $15.3 million, came on July 30. The market remained open after the June election because its resolution was tied to the formal swearing-in of the elected government.

The issue had surfaced previously in presidential markets. Barron’s reported in April that Polymarket international contracts on the 2028 election showed unusual low-odds activity, including lower volume on JD Vance becoming the Republican nominee than on Elon Musk, who is ineligible for the presidency. Similar patterns appeared in contracts on prospective Democratic nominees.

Wash trading involves traders colluding to buy and sell an asset in order to create a false impression of economic activity. Polymarket denied that wash trading or other inorganic trading explained the patterns. Kyle Gesuelli, the company’s head of revenue and analytics, said highly active traders, or “sharps,” use complex software and algorithms to exploit mispriced low-odds contracts, helping to bring pricing imbalances back into line.

Gesuelli said Polymarket’s international exchange has more such traders than its U.S. platform, where casual retail users play a larger role. Some other prediction-market observers suggested the international volume could instead be connected to speculation over a possible cryptocurrency-token airdrop. Polymarket, whose international platform runs on Polygon, declined to comment on that suggestion.

A Columbia University study first released in November 2025 found that patterns it deemed indicative of wash trading accounted for 60% of Polymarket international’s weekly volume in December 2024. That measure fell to 20% by October 2025 and, according to lead author Allen Sirolly, had declined to a negligible amount by April. Polymarket said expanded surveillance and the introduction of exchange fees had reduced the chance of manipulation.