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Sample collected 2026-09-24 · re-collected weekly · data and method below
Across 1,918 resolved Polymarket markets from 225 of the highest-volume events that closed between 2025-09-25 and 2026-09-21, prices a week before close lined up with what happened: in 9 of 10 price bands the gap between the average price and the share of outcomes that happened is within normal sampling noise (the exception: the 0–10% band, where outcomes happened more often than priced, 3.9% against 1.7%). Outcomes priced at 50% or more a week out happened 75% of the time (246 favourites). The overall Brier score is 0.089, but that is flattered by long shots that were clearly going to lose; on the 613 genuinely uncertain markets (priced 10–90%) it is 0.202, against 0.250 for always saying 50%.
Each dot is a price band; dots on the dashed diagonal mean perfect calibration. Dot size grows with the number of markets.
| Price band | Markets | Average price | Resolved Yes | Difference |
|---|---|---|---|---|
| 0–10% | 1,243 | 1.7% | 3.9% | +2.2 pts |
| 10–20% | 165 | 14.2% | 19.4% | +5.2 pts |
| 20–30% | 116 | 24.5% | 25.9% | +1.3 pts |
| 30–40% | 78 | 34.8% | 42.3% | +7.5 pts |
| 40–50% | 70 | 45.1% | 45.7% | +0.6 pts |
| 50–60% | 71 | 54.3% | 60.6% | +6.2 pts |
| 60–70% | 49 | 65.0% | 73.5% | +8.5 pts |
| 70–80% | 41 | 74.7% | 63.4% | -11.3 pts |
| 80–90% | 23 | 85.1% | 87.0% | +1.8 pts |
| 90–100% | 62 | 96.1% | 95.2% | -0.9 pts |
Every market in the sample is in the free data: JSON · CSV (CC BY 4.0, credit “PolymarketTrader” with a link). The long shots that came in are on the biggest upsets page. Score your own forecasts with the Brier score calculator.
Across 1,918 resolved Polymarket markets from 225 of the highest-volume events that closed between 2025-09-25 and 2026-09-21, prices a week before close lined up with what happened: in 9 of 10 price bands the gap between the average price and the share of outcomes that happened is within normal sampling noise (the exception: the 0–10% band, where outcomes happened more often than priced, 3.9% against 1.7%). Outcomes priced at 50% or more a week out happened 75% of the time (246 favourites). The overall Brier score is 0.089, but that is flattered by long shots that were clearly going to lose; on the 613 genuinely uncertain markets (priced 10–90%) it is 0.202, against 0.250 for always saying 50%.
A calibrated market's 70% outcomes happen about 70% of the time. The table groups outcomes by their price a week before close and shows how often each group actually resolved Yes.
We took the highest-volume Polymarket events that closed in the last 12 months, up to 15 of the most-traded outcome markets per event (at least $10,000 traded), read each market's price 7 days before it closed from Polymarket's public price history, and compared it with the final resolution. Markets that resolved 50-50 or had no price history at that time are excluded.
Polymarket View is independent and not affiliated with Polymarket. Educational analysis, not financial advice. All Polymarket odds · Statistics