By John Leslie

Prediction markets are booming. Polymarket alone processes billions in volume. But a fundamental question remains: when a market says there's a 60% chance of something happening, does that event actually happen 60% of the time?

I pulled 7,661 resolved binary markets from Polymarket's API, grabbed price history for the top 2,000 by volume, and built an interactive calibration tracker to find out.

Try it here: Polymarket Calibration Tracker

What is calibration?

A forecaster is well-calibrated if their predicted probabilities match observed frequencies. If you say "70% chance" for 100 different events, roughly 70 of them should happen.…