Stanford researchers clock Polymarket's 5-minute BTC contracts as a $1.28M pickpocket ⏱️

Researchers at Stanford University and Singapore Management University have concluded that Polymarket's five-minute Bitcoin prediction markets reward sophisticated traders who nudge spot prices at settlement, siphoning roughly $1.28 million from ordinary users during the studied period. The contracts let users wager on whether $BTC finishes above or below a preset level after each five-minute window, settling via Chainlink price feeds that read spot values at window close. That design, the authors wrote, gives well-capitalized traders a direct motive to push $BTC's spot price in the final seconds before settlement and unwind the move immediately after.

The paper analyzed order-flow data before and after Polymarket launched the contracts in July 2024 and documented sharp spikes in spot trading immediately before settlement followed by rapid reversals, a pattern the researchers said is consistent with settlement-price manipulation. Extending the contract duration from five minutes to 15 minutes "largely eliminated the effect," according to the study. The authors stopped short of declaring prediction markets inherently fragile, instead pointing to settlement design choices, including longer windows and time-weighted average pricing, as ways to blunt the behavior.

The findings carry implications beyond crypto. The paper notes that traditional exchanges including Nasdaq and Cboe have proposed event contracts tied to asset prices, raising the same design questions as prediction markets push further into regulated finance. The researchers argued contract structure, rather than the prediction-market format itself, is the lever that determines how exposed users are to manipulation.

The sector itself has continued to expand. Prediction markets posted record trading volumes in June as the expanded 2026 FIFA World Cup drew heavy activity, with DefiLlama data showing Kalshi processing about $9.4 billion and Polymarket International roughly $4.3 billion during the month. World Cup winner markets on the two platforms have since generated more than $5.4 billion in combined volume, with Polymarket at about $4.25 billion and Kalshi at about $1.2 billion, according to platform data.

That growth has arrived alongside legal challenges. Several US states have moved against operators including Kalshi and Polymarket this year, while the Commodity Futures Trading Commission has argued that federally regulated event contracts fall under its "exclusive jurisdiction" rather than state gambling laws. The dispute is working its way through the federal courts, and legal observers have said conflicting appellate rulings could eventually push the question of whether event contracts constitute gaming or financial instruments to the US Supreme Court.