How to read a market probability
70% means it doesn't happen three times in ten. That matters more than it sounds.
The most common mistake with market odds is treating the favourite as a sure thing. A candidate at 70% loses three times in ten. On Polymarket, Lula was at 16.5% a day before polls closed in Brazil's runoff (20:00 UTC, October 24), and he won.
Three ways to read a number
Under 20%: a long shot, not a no. Things at 15% happen about one time in seven. Markets that sit this low are often where the surprises come from.
40 to 60%: genuinely open. The market doesn't know, and small moves here mean less than they look.
Over 90%: close to settled, unless the rules hold a catch. A high price usually means the outcome is nearly certain, or that the market is waiting on an official step, like a result being certified.
Moves matter more than levels
A market going from 40% to 55% in an hour tells you traders learned something. A market drifting a point a day tells you very little. We flag a move only when it's sharp and real money traded on it. See the moves.
Check the size and the spread
Before you quote a number, look at how much has traded and how wide the gap is between buy and sell offers. Both are on every market page, under "About this market".
Markets can be wrong
A price is a crowd's estimate, not a forecast we make. Over many questions, well-traded markets tend to be about right on average, but any single price can miss. Our accuracy page tracks how settled markets did. Next: why prices and polls differ.