How prediction markets resolve: the rulebook that decides who was right

Most people learning about prediction markets focus on the price. That is the fun part — a number that moves, a crowd changing its mind in public. But the price only means something because of a promise at the other end: on some future date, this market will pay 100¢ to one side and 0¢ to the other, according to a rule written in advance.

That rule is called resolution, and it is the least glamorous and most important part of the whole design.

What resolution actually is

A prediction market share is a contract that pays out a fixed amount if a stated condition is met, and nothing if it is not. So every market needs three things settled before trading starts:

• The question — stated precisely enough that a stranger could judge it.
• The resolution source — the specific place the answer will be read from.
• The resolution date — when the answer gets read.

If a market says "Will inflation come down this year?", it is not tradeable. If it says "Will the Eurostat flash estimate for euro-area annual HICP inflation, published in January 2027 for December 2026, be at or below 2.0%?", it is. Same underlying curiosity, but the second version names a source, a number and a date, so there is nothing left to argue about.

Good market design is mostly this: converting an interesting question into a boring one.

Who decides — the three common models

A named external source. The cleanest approach. The market points at an official publication — a statistics office, a central bank release, a league's official results page, an election commission — and whatever that source says is the answer. Nobody's judgement is involved, which is the point.

The platform, against published rules. Regulated exchanges typically resolve markets themselves using rules filed in advance, with a regulator supervising the process and a formal route for complaints. You are trusting an institution, but a supervised one with rules on paper.

A decentralised oracle. Crypto-native platforms often outsource the decision to a token-holder voting system. Polymarket, for example, routes disputes to UMA's optimistic oracle: a proposed answer stands unless someone challenges it, and challenges escalate to a vote of token holders.

Each model trades one risk for another. External sources can be delayed, revised, or ambiguous about edge cases. Platforms can be accused of self-interest. Voting oracles can, in principle, reward whoever votes with the majority rather than whoever is factually right.

When the wording breaks: the suit that cost $240 million

In 2025 Polymarket ran a market on whether Volodymyr Zelenskyy would be photographed or videotaped "wearing a suit" before the end of June. At the NATO summit on 24 June he appeared in a dark tailored jacket and trousers that many outlets, and the garment's own designer, described as a suit. Others said it was not.

The market had drawn roughly $240 million in volume. It initially looked set to resolve Yes, was disputed, escalated through UMA's dispute process over about nine days, and finally resolved No — with a large share of total volume traded after the event had already happened, as people positioned on the dispute itself rather than on Zelenskyy's wardrobe.

The lesson is not that oracles are broken. It is that no resolution mechanism can rescue a badly written question. "Wearing a suit" felt obvious when the market launched and turned out to have no agreed definition. A market that had specified a source — say, a named wire service describing the outfit as a suit — would have settled in minutes.

What to check before you trade a market

Read the resolution criteria before you look at the price. Specifically:

1. Is a source named? If not, someone will have to use judgement, and you may not like whose.
2. What happens in the edge cases? Cancelled events, postponed elections, revised statistics, ties. Well-written markets say.
3. When exactly does it settle? "By the end of 2026" and "as reported in January 2027" are different contracts.
4. Who resolves disputes, and how long can that take? Your capital is tied up until it is done.

This is also why judging your own forecasting record requires the same discipline — we covered that in how to tell if a prediction was right. And once you can read resolution rules, the prices themselves get easier to interpret: see reading the odds.

The habit worth building

Experienced traders read the rules first and the price second. It sounds pedantic until the first time you are right about the world and wrong about the contract — a distinction that only exists because resolution is a written rule, not a general impression of what happened.

The good news is that this habit is free to practise. On Outcomer you trade with virtual money, so you can open a market, read its resolution criteria, take a position, and watch how the settlement actually plays out — without anything riding on it except your own track record. That is the cheapest possible way to learn the difference between being right and being paid.