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=136)
Polymarket (n=4548)
Bucket detail (Kalshi)
| Predicted bucket | n | Avg predicted | Actual YES rate | Error |
|---|---|---|---|---|
| 0–10% | 78 | 1.5% | 0.0% | -1.5pp |
| 10–20% | 5 | 14.4% | 20.0% | +5.6pp |
| 20–30% | 1 | 23.0% | 0.0% | -23.0pp |
| 30–40% | 1 | 32.0% | 0.0% | -32.0pp |
| 40–50% | 0 | — | — | — |
| 50–60% | 0 | — | — | — |
| 60–70% | 0 | — | — | — |
| 70–80% | 0 | — | — | — |
| 80–90% | 0 | — | — | — |
| 90–100% | 51 | 99.1% | 100.0% | +0.9pp |
Bucket detail (Polymarket)
| Predicted bucket | n | Avg predicted | Actual YES rate | Error |
|---|---|---|---|---|
| 0–10% | 2374 | 0.5% | 0.0% | -0.4pp |
| 10–20% | 43 | 13.5% | 0.0% | -13.5pp |
| 20–30% | 32 | 23.5% | 3.1% | -20.4pp |
| 30–40% | 30 | 34.8% | 6.7% | -28.2pp |
| 40–50% | 20 | 44.8% | 15.0% | -29.8pp |
| 50–60% | 24 | 54.3% | 8.3% | -46.0pp |
| 60–70% | 12 | 63.7% | 25.0% | -38.7pp |
| 70–80% | 6 | 74.1% | 16.7% | -57.5pp |
| 80–90% | 6 | 81.2% | 50.0% | -31.2pp |
| 90–100% | 1677 | 99.6% | 99.0% | -0.6pp |