Polymarket's "Fed Decision in September?" event is the platform's biggest market by 24-hour volume - $6.6M as of 2026-09-04 11:30 UTC - because the September 15-16 FOMC meeting is a genuinely open question, not a formality. "No change" trades 59.5c, up ten points on the day; "25 bps increase" trades 41.5c, down eight. A week ago the numbers were close to the opposite of that: "no change" had fallen to a 37.5c low and "25 bps increase" had climbed as high as 60.5c. The swing back traces to Fed Governor Christopher Waller, who told markets Thursday, September 3, that he could support holding rates steady - with a condition attached. Numbers below are from Gamma and the CLOB, fetched at that time.
01Why September is contestedA split committee, inflation still above target
The Fed has held its target range at 3.50-3.75% since December 2025, and the July 29 FOMC vote to hold again was 9-3 - the first split decision under Chair Kevin Warsh, with three regional bank presidents dissenting in favor of a hike. That's an unusual amount of open disagreement for a committee that normally moves as a bloc, and it's why this market trades real size on both a hold and a hike instead of clustering on one outcome the way most Fed-decision markets do. The dissent is about inflation, not growth: headline CPI is running 3.4% year-over-year with core at 2.5%, while the Fed's preferred PCE gauge sits at 3.7% - all still meaningfully above the 2% target more than three years into the tightening cycle. Warsh struck a hawkish tone on exactly that point at his Jackson Hole speech August 28, and this blog covered how the market reacted that day: "no change" and "25 bps increase" flipped to a 49.5c coin flip within the hour.
02The chartA round trip, then a reversal
Jackson Hole set the direction, and it kept going for three more days: "no change" slid from that day's 49.5c close to a 37.5c low on September 1, while "25 bps increase" climbed as high as 60.5c on August 31 - briefly the clear favorite. Then it reversed. Starting around 12:30 UTC on September 3, "no change" jumped from 48.5c to a 62.5c intraday high in about ninety minutes, and has held a high-50s to 59.5c band since. "25 bps increase" gave back the same ground, settling in the low-to-mid 40s.
03What Waller saidPatient, with a two-week condition
The catalyst was Fed Governor Christopher Waller, who indicated he'd support holding the policy rate at the September meeting - provided the recent disinflation trend holds up in the data still to come. He put it directly: "If this continues in the data due over the next two weeks, I would be inclined to support holding the target." That data is the August CPI report, due in the days before the September 15-16 meeting and not yet released as of this writing - which is why Waller's comment reads as conditional rather than settled. He also wasn't fully dovish: inflation remains "meaningfully above" target in his own description, and he warned that "it may not take much acceleration in inflation" to change his mind. CME's FedWatch tool, which tracks Fed funds futures rather than an event contract, showed September hike odds dropping about 12 points to roughly 54.6% on the news - a smaller, futures-market version of the same move Polymarket's contract-based pricing shows.
That's the shape of this market in one sentence: two Fed officials gave two speeches eight days apart, one hawkish and one conditionally dovish, and the September contract round-tripped about 20 points and back on nothing but words - no data release moved it either time. The next input that actually is data lands with the August CPI print, and Waller has already told the market exactly how he'll read it.
04The full ladderFive outcomes, two of them live
Polymarket splits the September decision into five brackets. Three are effectively dead - a 50+ bps move in either direction, or a 25 bps cut, all price under a penny, reflecting how far outside the realistic range they sit. The real market is a two-way split between a hold and a quarter- point hike:
SEPTEMBER FOMC OUTCOME PRICE 24H
Decrease 50+ bps 0.15c --
Decrease 25 bps 0.65c +0.1c
No change 59.5c +10.0c
Increase 25 bps 41.5c -8.0c
Increase 50+ bps 0.45c -0.2c
Add "no change" and "25 bps increase" together and they sum to 101c, close enough to par that the book is pricing this as genuinely binary - almost no money is left on the three tails. Liquidity is deepest on "no change" ($263K) and thinnest by comparison on the far-out-of-the-money legs, which is normal for a bracket ladder once two contracts have absorbed nearly all the probability mass.
05Watching it from hereOne number left to move it
Markets like this one are why a rate-decision event is worth watching on a screen that shows the whole ladder, not just the headline contract - the interesting signal here was never "no change" alone, it was how fast money moved between it and its mirror image on nothing but a speech. polymarket-tui lists every leg of an event like this with live price and 24-hour move in one table, so a reversal like Wednesday's reads as a wave across the ladder rather than five separate lookups.
$ uv tool install polymarket-tui
$ polymarket-tui
No account is needed to browse markets, books, and charts. The install page has Homebrew and one-liner options.