Why the outcomes add up to more than 100
In a multi-outcome event the YES prices rarely sum to exactly one dollar. The gap is a cost, the structure underneath links every outcome together, and both matter under a per-event cap.
Open any event with more than one outcome and add up the YES prices. The total is almost never exactly 100. It is usually a little over, sometimes a lot over, and the amount it is over tells you something about what it costs to trade there.
A live example makes it concrete. Your Call evaluations trade Polymarket, and around midday Eastern on 5 October 2026 the event on which party will control the US Senate after the midterms was quoted like this:
| Outcome | Best bid | Best offer | Midpoint |
|---|---|---|---|
| Democratic Party | 67 | 68 | 67.5 |
| Republican Party | 33 | 34 | 33.5 |
| Sum | 100 | 102 | 101 |
Those prices will have moved by the time you read this. The structure will not have, and the structure is the point.
Three different sums
The offers add to 102. If you bought one YES share of each party at the best offer, you would pay $1.02 for a pair of shares that pays at most $1.00 at resolution. That is a guaranteed loss of two cents before any fee, and it is the cost of buying the whole field at once.
The bids add to 100. If you already held one of each and sold them into the best bids, you would get exactly $1.00 back.
The midpoints add to 101. The displayed figure on a market is the midpoint of the spread, per the venue’s help documentation, so the tiles read 68 and 34 after rounding. On screen, the field looks like it adds up to 102 because two half-cent midpoints both rounded up.
The difference between the offer sum and the bid sum is just every outcome’s spread added together. In a two-outcome event with one-cent spreads that is two cents. In a hypothetical eight-candidate field where each candidate is quoted one cent wide, it is eight cents, and that is before any of the thin, wide long-shot markets that crowded fields usually carry.
Why the sum cannot drift far below 100
If the offers ever added to less than one dollar, buying every outcome would lock in a profit, because exactly one of them has to pay. Anyone watching would take that trade until the prices moved back. If the bids added to more than one dollar, the mirror trade would do the same. So the offers tend to sit at or above 100 and the bids at or below it, and the gap between them is where the cost of trading lives.
Every outcome is connected underneath
A multi-outcome event looks like a list of separate YES/NO markets. On the venue it is not quite that. Its documentation describes these as negative risk markets, built on one operation: a NO share in any market in the event can be converted into one YES share in every other market in the event.
Holding NO on one party is therefore the same economic position as holding YES on every other outcome. That conversion is what keeps the prices across an event tied together, and it produces a detail worth noticing in the snapshot above.
The venue’s help documentation explains that a YES order and a NO order whose prices add to $1.00 match against each other. So a resting YES bid at 33 on the Republican market is, in effect, a NO offer at 67. Compare the two ways of expressing the same view:
- YES on the Democratic Party at 68. Pays if Democrats control the chamber.
- NO on the Republican Party at 67. Pays if Democrats control it, and also if any other outcome is certified.
In that snapshot, the second route cost a cent less and paid in strictly more cases. A cent is small. On a position sized to the per-event cap it is not nothing, and it costs only the habit of checking both sides before you click.
The outcomes you cannot see
The same event also carried a set of unnamed placeholder outcomes and an “Other” outcome, none of them with any bids. The documentation describes this as augmented negative risk: placeholders exist so that outcomes which emerge after launch can be added without restructuring the event, and if the correct answer is never named, the market resolves to Other.
The guidance there is direct. Trade only named outcomes, and ignore placeholders until they are named or the event resolves, because what Other means can change as placeholders are filled in. A question that reads as a two-way choice can have more slots underneath it than the screen shows.
What this means inside an evaluation
One event, one cap. Maximum profit from any single event is 0.5% of account size, and every market inside an event aggregates against that one ceiling. YES on one candidate and NO on another are two tickets and one cap. Max Profit Per Event, explained shows a rejection where exactly that happened.
The band trims the field. Opening orders are accepted between 0.20 and 0.80. In a crowded event, most long shots sit below 20, which puts YES out of range, and their NO sits above 80, which puts that out of range too. What you can open is usually the handful of contenders in the middle.
Buying the field is a cost, not a hedge. Spreading across every outcome in an event pays the offer-side overround on each one, and the commission on each one. The commission is charged on cost basis — what you actually pay for the shares, not what they would be worth at settlement — so every extra leg adds to it. Inside a single event, the most you can keep is still the one capped amount.
Check both doors. When two routes express the same view, the cheaper one is not always on the side of the market you opened first. The book is the place to look, not the tile, and the number on the tile covers why.
None of this is a reason to trade multi-outcome events or to avoid them. It is what the prices in them are made of, and it is all visible before the order.
Evaluations are conducted on simulated accounts. Not financial advice.