Event contracts and futures favor a rate increase, but quoted readings range from 73% to 90%. Different timestamps, spreads and contract terms complicate the comparison.
Going into Wednesday's Federal Reserve decision, every venue that prices it agrees on the direction. None of them agrees on the confidence.
Polymarket's contract showed 79% for a 25 basis point hike against 21% for a hold, on roughly $146 million of total volume, with about $30 million and $39 million of volume in the two principal legs.
An aggregated reading across six venues, including Polymarket, Kalshi, ForecastEx and Gemini, produced 79.4% for a hike and 20.7% for a hold, with individual platform readings spanning 75.5% to 80%.
Robinhood's own contract on the decision priced meaningfully lower. It showed a 25 basis point hike at 73 cents, a hold at 29 cents, a 25 basis point cut at 3 cents, a larger hike at 3 cents and a larger cut at 2 cents.
Traditional fed funds futures have run higher than all of them, with readings quoted through the week in the mid-80s to roughly 90%.
The spread is the anomaly
The quoted readings span 17 percentage points between the lowest event-contract price and the highest futures-implied estimate. They were collected at different times, so the gap is not a synchronized measure of disagreement or an established arbitrage opportunity.
The Robinhood legs also sum above 100, at 110 cents across five outcomes, which is normal for a quoted contract set carrying a spread but means the 73 cent figure is not directly comparable to a normalized probability from a venue quoting differently.
That accounts for part of the gap. It does not obviously account for all of it, and it does not account for the gap between event contracts near 79% and futures near 88%.
What the gap is made of
Three explanations are available. Event-contract venues and rate futures attract different participants with different funding costs, and the capital required to arbitrage an 8 point difference on a two-day binary is not trivially cheap. Retail-facing venues carry wider spreads that compress the implied probability of the favored outcome. And the contracts are not always specified identically, with some resolving on the target range and others on a specific increment.
Why it is worth watching past Wednesday
The Federal Reserve decision is the cleanest resolution event these venues will price all quarter. It is scheduled and publicly observable, although the listed contracts include several possible rate outcomes. If a 17 point spread persists into a question this clean, that says something about how much price discovery these markets are actually performing on the harder questions they also list, where no resolution date forces convergence.
Wednesday afternoon produces a result. The more useful data is which venue was closest, and whether the same one is closest next time.