Opinion: If a single trader can manipulate and predict market outcomes, that market should not be listed for trading.

As prediction market platforms like Polymarket gain mainstream attention during US election cycles and geopolitical events, their prices are increasingly cited as real-time signals. However, this premise fails when contracts create economic incentives for participants to alter the outcomes they measure. The core issue lies in product design, not volatility. When an outcome can be achieved by a single actor through a single action, the contract transforms from a predictive tool into an execution script. The article cites Super Bowl stadium crash betting as an example, pointing out that traders have actually performed this action after betting "yes." Political and event-driven markets are particularly vulnerable because they often rely on discrete nodes that can be influenced at low cost and have low liquidity. If participants begin to suspect that outcomes are being manipulated, the platform will lose credibility. The article argues that the sports market, due to its high visibility, multi-layered governance, and multi-party participation structure, is more difficult to manipulate at the individual level and should serve as a structural reference. Prediction market platforms should establish clear listing standards to exclude contracts that can be manipulated at low cost by a single participant or that constitute a bounty for harm; otherwise, external regulation will intervene.