A prediction market turns expectations about a future event into a changing price. On a binary market, that price is commonly read as a probability: a price near 60 cents suggests roughly a 60% chance of the specified outcome. It is a useful signal, not a promise. To understand a Polymarket number, read the contract, check how the displayed price was formed, and ask what information the market has absorbed.
What is a prediction market?
Participants trade contracts whose payoff depends on an outcome. Polymarket describes binary outcome shares that pay $1 for the winning side on resolution. A trader who thinks the quoted odds underestimate an outcome can express that view through a trade. Other participants can disagree. The changing price is the result of those interactions, rather than a pollster asking a fixed sample for its opinion.
The forecasting attraction is information aggregation. Someone may follow a legislative timetable, another may understand an industry, and another may notice a change in public data. A market gives them a common question and a mechanism for acting on different judgments. That does not mean every market has enough independent information or that every participant is well informed.
How to read Polymarket odds
Distinguish the number on the page from a price you could actually trade. Polymarket says its displayed probability normally uses the midpoint between the best bid and ask; if the spread exceeds ten cents, it uses the last traded price. The bid, ask and last trade can therefore tell different stories. The platform's price-calculation documentation is the source for that convention, not a guarantee that an executable trade exists at the displayed number.
Here is an illustrative example, not a live market: the best buyer offers 54 cents and the best seller asks 60 cents. Their midpoint is 57 cents. Reading that as approximately 57% may be reasonable as a summary of the order book, but a buyer cannot assume a purchase at 57 cents. A wide spread or a small amount available at the best price should make you more cautious about treating the headline number as a precise consensus.
The rules define the event, not just the headline
Two markets with similar titles can predict different events. One might concern an announcement before a deadline; another might require a policy to take effect. The resolution source may use a particular publication, official statement or measurement. Polymarket's clarification guidance explicitly distinguishes a market title from the rules that determine resolution. Read those rules before comparing the price with your own forecast.
- Identify the exact outcome and deadline, including any time zone.
- Read the specified resolution source and provisions for unusual outcomes.
- Check when the price was observed and whether there has been material news since then.
- Inspect the bid-ask spread and available liquidity, not just a percentage or volume total.
- Compare like-for-like questions before claiming two platforms disagree.
Are prediction markets accurate?
Accuracy is a property of a track record, not of the word market. A 70% favorite sometimes loses without proving that 70% was unreasonable. Conversely, a successful 99% call may add little information on an easy question. Evaluate probabilities across resolved questions at comparable lead times, including misses and difficult cases. Our guide to Brier scores and calibration explains how to do that.
A fair comparison also needs matching outcomes and scoring conventions. Brier.fyi describes matching questions and accounting for forecast timing when assessing platforms. The Hypermind comparison with Polymarket and Kalshi illustrates the limits of comparing different question sets: lower reported scores do not, by themselves, establish a universal winner.
Markets, polls and AI answer different questions
An opinion poll estimates what respondents say they prefer or intend to do. An event market estimates how its contract will resolve. An AI forecasting system produces a probability from its evidence and model process. They can inform the same decision, but they are not interchangeable measurements. Poll movement, election rules and turnout may help explain a market price without making that price a poll of voters.
For an analyst, the productive next step is to use a market as a reference point and investigate any disagreement. AI forecasting versus prediction markets sets out a comparison workflow. The Forecasting Machine belongs to this evidence-based forecasting discussion; it should not be described as a Polymarket exchange, an affiliated service or a guaranteed trading advantage.
This guide is about interpreting forecasts, not recommending a trade. Financial exposure, platform access and legal eligibility are separate questions. Neither a market price nor an AI estimate removes uncertainty or guarantees a profitable outcome.
