Prediction Market Calibration Scorecard
How accurate are Kalshi and Polymarket prices, empirically? We bucket every resolved market in the last 365 days by its final pre-close YES price (0–10%, 10–20%, ...) and compare the bucket's predicted probability to the realized win-rate. A perfectly calibrated venue sits on the diagonal.
Overall
Kalshi (n=49980)
Polymarket (n=19856)
Bucket detail (Kalshi)
| Predicted bucket | n | Avg predicted | Actual YES rate | Error |
|---|---|---|---|---|
| 0–10% | 26136 | 1.1% | 0.1% | -1.1pp |
| 10–20% | 452 | 13.8% | 2.0% | -11.8pp |
| 20–30% | 229 | 24.0% | 4.8% | -19.2pp |
| 30–40% | 137 | 33.9% | 7.3% | -26.6pp |
| 40–50% | 90 | 44.1% | 11.1% | -33.0pp |
| 50–60% | 80 | 54.1% | 31.2% | -22.9pp |
| 60–70% | 68 | 64.7% | 67.7% | +3.0pp |
| 70–80% | 90 | 75.1% | 85.6% | +10.5pp |
| 80–90% | 203 | 84.9% | 93.6% | +8.7pp |
| 90–100% | 22495 | 99.0% | 99.7% | +0.7pp |
Bucket detail (Polymarket)
| Predicted bucket | n | Avg predicted | Actual YES rate | Error |
|---|---|---|---|---|
| 0–10% | 9873 | 1.1% | 0.1% | -1.0pp |
| 10–20% | 764 | 13.8% | 0.8% | -13.0pp |
| 20–30% | 432 | 24.0% | 2.5% | -21.4pp |
| 30–40% | 279 | 34.3% | 3.2% | -31.0pp |
| 40–50% | 263 | 44.3% | 6.1% | -38.2pp |
| 50–60% | 217 | 53.5% | 10.6% | -42.9pp |
| 60–70% | 131 | 64.1% | 15.3% | -48.8pp |
| 70–80% | 70 | 74.7% | 35.7% | -39.0pp |
| 80–90% | 69 | 83.8% | 40.6% | -43.3pp |
| 90–100% | 7439 | 99.6% | 99.2% | -0.4pp |