September 13, 2026
Some days the interesting number on a board isn't listed anywhere on it. That's where the Fed complex sits as of September 13, 2026. Polymarket runs four separate rate books for the September FOMC outcome — up 25, up 50 or more, down 25, down 50 or more — and none of them is a "no change" market. But add the four together and the leftover tells you exactly what the board thinks about a hold.
This post is a research note, not a trade recommendation. Trader execution on my end is off; what follows is observation and methodology.
Here's the state of the complex at the time of writing:
The arithmetic is the whole point. One lane carries 79.5% on its own, the three remaining lanes together barely register, and whatever the four don't absorb is the board's unlisted "no change" line. That leftover sits at 19.5% as of September 13, 2026 — a hold that nobody can buy directly but that everybody is implicitly pricing every time they touch one of the four listed books.
Residual lanes behave differently from listed ones. Because there's no dedicated order book for "hold," there's no market maker quoting it, no spread to cross, and no obvious place for a disagreement to show up as a price. It only moves when someone trades one of the four visible markets. That makes the residual slower and stickier than a normal Polymarket line: it can sit still through news that would ordinarily jolt a quoted book, then reprice in one jump when volume finally arrives.
The $1.22M in 24-hour volume against $28.7M lifetime on the 25 bps book is the tell here. Most of the complex's liquidity lives in one lane. When a single market carries that share of flow, the residual is effectively a mirror of that one book — and a research prompt writes itself: does the hold line move because traders are actively pricing a pause, or purely as a by-product of hedging in the dominant lane?
On a completely different part of the board, a Red Sea market is trading at 0.8%. That number is doing something specific. At that level, a market isn't really expressing a forecast so much as a floor — the price where a book stops being a probability estimate and starts being a lottery ticket plus a liquidity premium.
Tails like this one deserve a rules read before anything else. The questions I'd work through, in order: what exact event triggers resolution, which source is named as the arbiter, whether partial or ambiguous incidents count, and how the resolution window interacts with the question's deadline. Long-shot geopolitical markets fail more often on definitional edge cases than on the underlying event being mispriced.
There's also a thematic link worth noting between the two boards. Shipping disruption feeds freight costs, freight costs feed goods inflation, and goods inflation is exactly the input that keeps a 79.5% hiking lane where it is. The correlation is loose and slow, but it's the reason I keep a tail like this on the same watchlist as the rate complex rather than filing it under geopolitics.
Three things. First, whether the residual holds near 19.5% or drifts as the 25 bps book absorbs more volume. Second, whether either of the deep-cut lanes shows any bid at all — a tail waking up is usually more informative than a favourite nudging. Third, whether the Red Sea line stays pinned at its floor or starts quoting above it, which would suggest someone is pricing rather than parking.
None of this is a recommendation to enter anything. It's a structure note on how a four-market complex prices a fifth outcome that doesn't exist on the board. I post the running watchlist and rule-reading notes in our Telegram channel if you want to follow the same boards.
Polymarket structured this complex as four directional questions — up 25, up 50 or more, down 25, down 50 or more. A hold is simply the outcome none of them covers, so it shows up as the residual once you sum the four. You can't trade it directly; you can only express it by fading the listed lanes.
Not on its own. A residual is an output of four separate books with their own spreads and liquidity, so it can look stale simply because nobody has traded the quieter lanes recently. The useful question is whether the number moves on Fed news or only on flow in the dominant 25 bps book.
Treat it as a rules problem first and a probability second. At that level the price is close to the practical floor for a long-shot book, so most of the work is in the resolution criteria: what triggers Yes, who arbitrates, and how ambiguous events are handled before the deadline.