FOMC Tracker

Polymarket's September book turned $4,266,363 in the last 24 hours—the largest macro book listed anywhere, and seven and a half times Kalshi's $570,974 on the same meeting. That book had been missing from this page. It is the anchor now.

What it shows is worth the correction. $2,985,858 of that $4.27M—70% of the entire day—went through two legs the book prices at 1.3% and 0.5%.

• 25 bps decrease at 1.3% took $1,555,290, the deepest leg in the book, more than double the flow on the 68.5% favourite.
• 50+ bps increase at 0.5% took $1,430,568.
• No change at 68.5% took $690,316. 25 bps increase at 30.5% took $482,589.

Kalshi is the same shape at a seventh the size: Cut 25bps at 0.5% took $264,578, essentially matching the 67.5% hold leg's $250,508—and more than four times the 31.5% hike leg's $57,598.

Two exchanges, two order books, one pattern. The meeting is priced as hold-or-hike, and almost all of the money is trading a cut neither book believes in. On levels the two agree to within a point: 67.5% and 68.5% on a hold, 31.5% and 30.5% on a 25bp hike.

September 16, across all three exchanges. Kalshi and Polymarket agree to within a point on both live outcomes; Manifold, on $163 of daily volume, prices the hold slightly higher at 70.9% and the hike lower at 23.6%.

Kalshi's open interest is where the size actually sits: $3,474,820 on the hold, $2,896,353 on a 25bp cut, and $1,737,284 on the hike. The cut leg—priced at half a percent—carries 83% as much open interest as the outcome the book calls a two-in-three favourite.

The half-percent leg that will not stop trading, next to the post-meeting rate ladder.

There is no obvious reading of Cut 25bps at 0.5% taking $264,578 on Kalshi and $1,555,290 on Polymarket that makes it a directional view—at those prices, the expected payoff requires the market to be wrong by a wide margin. The more likely explanations are hedging against a shock, or market makers working both sides of a leg that costs almost nothing to quote. Either way it is the most-traded contract in US macro right now, and it is priced at a rounding error.

The path to December, where the same pattern repeats at a larger scale.

Kalshi's cut-count Range puts exactly 0 cuts at 86.3% and holds $1,004,114 there. But look down the tail: exactly 2 cuts (2.1%) holds $392,218, exactly 4 cuts (0.5%) holds $317,836, and exactly 14 cuts at 0.4% holds $315,717—and that fourteen-cut leg took $5,300 in the last day, nearly twice the flow on exactly 1 cut at 9.2%.

Open interest across rungs 2 through 14 is close to uniform at roughly $260k–$390k apiece, on a book that prices every one of them under 2.1%. That is not thirteen independent views about the rate path; it is a seeding or market-making pattern, and it is worth naming as such rather than reading as signal.

Polymarket's separate Fed rate hike in 2026 contract sits at 55.5% on $184,436—a coin flip on a hike happening sometime this year against a 31.5% chance of it happening at this meeting.

• The Polymarket September book is now the one to watch, not Kalshi's. $4.27M against $571k. Any time this page's two anchors diverge, the deeper book is the better read.
• The 1.3% cut leg. It has taken $1.5M in a day. If it starts to firm rather than just trade, that is the first real signal of a policy surprise.
• The hold/hike split holding at roughly 68/31 on both exchanges. That agreement has been stable. A break in it—either venue moving three points alone—is more informative than either book's level.
• Kalshi's $2.9M of open interest on the cut. It is 83% of the open interest on the favourite. Whatever that position is, it unwinds on September 16.
• The fourteen-cut rung. Not a signal. Included because the cut-count book's tail is uniformly seeded and readers should know that before drawing conclusions from its shape.
• Polymarket's 55.5% on a 2026 hike. Reconciling that with 31.5% at September implies roughly a one-in-three chance of a hike at one of the two remaining meetings after it.