PREDICTION MARKET TOOLS
Prediction Calibration Journal
Record your forecasts locally, resolve questions and measure your Brier score without an account.
Make a forecast, then check it
Write a specific YES/NO question with a deadline and resolution source. Your question and probability stay in this browser; clearing site data removes them.
Brier score: Resolve a forecast to start · 0 resolved
Score = mean of (forecast probability − outcome)², with YES = 1 and NO = 0. Lower is better; 0 is perfect, 0.25 is the score for always predicting 50%. Small or selectively resolved samples do not establish forecasting skill. This journal does not independently verify outcomes.
Build a forecasting habit
Choose questions that can be resolved objectively, record your probability before the deadline, and resolve every forecast, including the awkward ones. Keep the original forecast when new evidence changes your mind; make a new entry if you want to compare the update.
Brier scores measure squared probability error. They mix calibration and discrimination: compare performance on similar questions over enough observations rather than treating a small score change as proof of skill. Export your journal periodically if you want a backup.