US Open: Did Kalshi's Prediction Markets Get It Right?
PokerNews stress-tests Kalshi's probabilities across all 254 US Open singles matches.
Kalshi's prediction markets called 254 US Open singles matches this month — and a PokerNews analysis published September 18, 2026 put those probabilities under the microscope to see how well they held up.
Why It Matters
Prediction markets live or die by calibration: if a market assigns 70% probability to an outcome, that outcome should materialize roughly 70% of the time across a large sample. A 254-match sample from a single Grand Slam is a meaningful stress test — large enough to reveal systematic bias but small enough that variance still plays a role. For bettors, a well-calibrated market means the prices are honest benchmarks, not invitations to fade. For the prediction-market industry, which is fighting for regulatory legitimacy in the United States, demonstrated accuracy strengthens the case that these platforms produce genuine price discovery rather than glorified gambling interfaces. Gambling involves real financial risk, and no calibration study changes that.
Context
Kalshi received CFTC authorization to operate event contracts in the United States, making it one of the few regulated prediction markets available to American users as of September 2026. Tennis has emerged as a high-volume category on the platform because match outcomes are binary, markets resolve quickly, and the sport's global schedule provides near-continuous liquidity. The US Open, held annually in Flushing, New York, is one of four Grand Slam events and draws the sport's deepest fields — making it a natural proving ground for probabilistic modeling.
What's Next
The full PokerNews methodology and match-by-match accuracy breakdown is available at pokernews.com. Kalshi's next major tennis calibration test arrives at the Australian Open in January 2027, which will provide a second large-sample data point to track whether any pricing biases identified here persist.
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