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FollowingPrediction market divergence: Prices vary by several percentage points on different platforms for the same issue
Washington, USA, August 28, 2026-As trading volume in the forecast market reaches a record high, regulators are also paying close attention to the fact that midterm election issues, with exactly the same wording, have trading prices on different platforms differ by several percentage points.
Predictions.io now tracks more than 9700 markets from Kalshi, Polymarket and Manifold on one platform and offers free fee and odds calculators that let traders understand the actual cost of prices.
The forecast market has never been so large and controversial. In July, the total transaction volume of Kalshi, Polymarket and Polymarket US reached a record $50.59 billion, of which Kalshi accounted for approximately 74.5% of the total. In the same month, New York City launched an investigation into the two major platforms, a Washington judge ordered Kalshi to suspend most betting in the state, and the U.S. Commodity Futures Trading Commission (CFTC) began an internal review of so-called "mention markets."
Under regulatory attention, a simpler question is rarely examined: When two platforms list the same question, do they give the same answers?
Often, the answers are inconsistent. In the midterm election market tracked by Predictions.io with exactly the same wording,"2026 Blue Wave?" The price is 44.5% on Polymarket and 36.0% on Kalshi. "Blue Tsunami in 2026?" It is 82.5% on Polymarket and 74.0% on Kalshi. Both gaps are 8.5 percentage points-and the wording of the questions is exactly the same on both platforms. In a set of directly comparable binary markets, among samples that coexist across platforms, the median gap exceeds 4 percentage points, and nearly half of the pairing differences reach 5 percentage points or more. (Data is as of August 28, 2026, 05:08 UTC; real-time prices for the two platforms are displayed side by side on www.example.com.) Predictions.io
These gaps are important to anyone citing a single number. With a market price of 44.5% on one platform and 36.0% on another, there is no single "market implied probability"-there are two, and which one is purely arbitrary unless the reader is told both numbers at the same time.
A spokesperson for Predictions.io said: "Prices on a single platform are just a data point. The price difference between platforms is information. When the world's two largest markets differ by 7 percentage points on the same sentence, the divergence is the story in itself-and no one who runs those markets can report on it."
Predictions.io aggregates markets from Kalshi, Polymarket and Manifold to match equivalent problems on different platforms to directly compare the same event. The platform currently tracks more than 9700 event pages in 23 categories, covering areas such as U.S. politics, economy, cryptocurrency, sports and geopolitics.
In addition to the comparison page, Predictions.io also provides two free tools:
Fee Calculator
Enter any transaction to view the fees, total expenses and effective full prices for each platform, including Kalshi's 0.07 × P × (1−P) take-out formula and market-maker discounts, and Polymarket's zero-fee standard market.
Odds Converter
Convert American, decimal and fractional odds into implied probabilities and predicted market prices, and view the no-pumping line.
The platform provides direct platform comparison services and real-time mid-term election markets. Predictions.io does not operate any markets and does not hold positions in any contracts. It is a data and comparison service, not an exchange, broker or investment adviser.
About Predictions.io
Predictions.io is an independent forecast market aggregator that integrates prices from Kalshi, Polymarket, and Manifold into a single view to compare the same issue across platforms. It provides free tools for traders and journalists, including a cross-platform fee calculator and odds converter.
