How to read a Brier score
The Brier score is the average squared distance between what you said would happen and what did. Say 70% for something that occurs and you take a penalty of 0.09; say 70% for something that does not and the penalty is 0.49.
Squaring is the whole design. It makes confident errors far more expensive than cautious ones, which is what stops a forecaster from improving their score by forecasting 99% on everything.
The benchmark that matters
A forecaster who answers 0.5 to every question scores 0.25 without knowing anything. Any score above that is worse than refusing to have an opinion, and plenty of confident forecasting records land there.
Applied to a market rather than a person, the Brier score of the closing price is the standard measure of how well prediction markets forecast. It is also the fair comparison for a trader who claims to beat the market: same questions, same scoring rule.
Where 0xinsider uses the Brier score
Trader profiles show a Brier score on the Forecast Accuracy card, beside a calibration edge. These metrics describe different aspects of forecasting. For a single trade, closing line value compares your entry price with the price the market closed at.
