Kalshi and Polymarket Fed hike odds reach 81% after hot August CPI
Prediction markets repriced sharply after August CPI data came in hotter than expected. As of September 14, traders on Kalshi priced a 79% probability of a 25-basis-point Federal Reserve rate hike at the September 16 FOMC meeting. Polymarket showed similar odds at 81.3%. Both platforms moved in tandem on the inflation surprise, with no-change odds falling to 19% on Kalshi. The repricing landed just two days before the scheduled Fed announcement.
The 20-point jump in hike odds over 48 hours tests whether these platforms can hold macro-trader trust through the actual Fed announcement. Thin liquidity in precise increment contracts has already shown it amplifies modest order flow into wild price swings, as when Polymarket's 25-basis-point contract dropped ten points in a single day last week.
Traders who bought at 61% now sit on paper gains that could evaporate just as fast if the Fed holds and odds collapse. Kalshi and Polymarket are competing directly for the same rate-positioning capital, and neither has yet proven book depth steady enough to prevent snapback. The platform that holds its price through Powell's press conference wins recurring macro flow beyond election cycles.
Joins a cluster of recent Fed-odds repricings that have together pushed prediction markets toward the front of macro-trader workflow, with Kalshi and Polymarket now regularly moving in lockstep on rate policy after nearly $200M in volume on a single decision.