PANews reported on November 8th that, according to Coindesk, a new study from Columbia University suggests that nearly 25% of Polymarket's trading volume may be fraudulent, involving users rapidly buying and selling contracts—typically to themselves or with colluding accounts—to inflate trading activity metrics without altering its net market position.

The study found that fraudulent trading peaked in December 2024, accounting for nearly 60% of weekly trading volume, and continued until October 2025. The sports and election markets were most affected. In some weeks, over 90% of the trading in these categories appeared to be fraudulent. Researchers suggest that the purpose of fraudulent trading may have been to manipulate future incentive mechanisms rather than for profit.