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Sample collected 2026-11-06 · re-collected weekly · data and method below
Across 1,871 resolved Polymarket markets from 224 of the highest-volume events that closed between 2025-11-08 and 2026-11-04, 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, 3.7% against 1.7%). Outcomes priced at 50% or more a week out happened 75% of the time (247 favourites). The overall Brier score is 0.088, but that is flattered by long shots that were clearly going to lose; on the 603 genuinely uncertain markets (priced 10–90%) it is 0.201, 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% | 1,206 | 1.7% | 3.7% | +2.1 pts |
| 10–20% | 159 | 14.3% | 18.2% | +4.0 pts |
| 20–30% | 115 | 24.5% | 27.0% | +2.4 pts |
| 30–40% | 76 | 34.8% | 40.8% | +6.0 pts |
| 40–50% | 68 | 45.1% | 45.6% | +0.5 pts |
| 50–60% | 70 | 54.3% | 61.4% | +7.1 pts |
| 60–70% | 52 | 65.0% | 75.0% | +10.0 pts |
| 70–80% | 41 | 74.9% | 63.4% | -11.5 pts |
| 80–90% | 22 | 84.9% | 86.4% | +1.4 pts |
| 90–100% | 62 | 96.0% | 95.2% | -0.9 pts |
On the 1,336 markets with a price at all three points, accuracy improves steadily as the close approaches: the Brier score is 0.087 a month before close, 0.064 a week before and 0.048 a day before (lower is better), and favorites won 65%, 82% and 82% of the time.
| Price taken | Markets | Brier score | Favorites won |
|---|---|---|---|
| 30 days before close | 1,336 | 0.087 | 65% of 164 |
| 7 days before close | 1,336 | 0.064 | 82% of 159 |
| 1 day before close | 1,336 | 0.048 | 82% of 188 |
Among categories with at least 20 genuinely uncertain markets, Politics & Elections markets were the most accurate a week before close (Brier 0.192 on 159 markets priced 10–90%) and Economy & Fed markets the least (0.246 on 23). Some categories have only a few dozen uncertain markets, so read differences of a few hundredths as noise.
| Category | Markets | Brier score | Brier, uncertain markets (count) | Favorites won |
|---|---|---|---|---|
| Politics & Elections | 663 | 0.080 | 0.192 (159) | 83% |
| Sports | 617 | 0.125 | 0.208 (328) | 64% |
| Crypto | 275 | 0.066 | 0.208 (52) | 85% |
| Tech & AI | 97 | 0.016 | 0.069 (9) | 100% |
| Economy & Fed | 89 | 0.064 | 0.246 (23) | 85% |
| Culture & Entertainment | 83 | 0.023 | 0.058 (16) | 100% |
| Geopolitics & World | 47 | 0.171 | 0.282 (16) | 100% |
Brier scores use the price a week before close. Categories with more long shots score better overall, so the uncertain-market column (prices 10–90%) is the fairer comparison.
Within this sample, more trading made no clear difference: on genuinely uncertain markets (priced 10–90% a week out) the quarter with the least volume ($28.1K to $1.14M) scored 0.192 and the quarter with the most ($7.33M and up) scored 0.208. Every market here already traded at least $10,000, so this says nothing about thinly traded markets.
| Lifetime volume | Markets | Brier score | Brier, uncertain markets (count) | Favorites won |
|---|---|---|---|---|
| $28.1K – $1.14M | 467 | 0.094 | 0.192 (171) | 76% |
| $1.15M – $2.64M | 468 | 0.083 | 0.197 (118) | 70% |
| $2.65M – $7.33M | 468 | 0.088 | 0.207 (168) | 77% |
| $7.33M – $375.81M | 468 | 0.088 | 0.208 (146) | 77% |
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; how long markets take to settle is in the resolution-time study; how long shots are priced is in the longshot-bias study. Score your own forecasts with the Brier score calculator.
Explained in plain words: can a 90% favorite lose?
Quoting this study in an article, a paper or a newsletter? Copy this citation and keep the date, because prices move. Tips: how to cite Polymarket odds.
Polymarket View, “How accurate is Polymarket?”, November 9, 2026, https://polymarkettrader.com/odds/accuracy/ (data: Polymarket, CC BY 4.0).
Across 1,871 resolved Polymarket markets from 224 of the highest-volume events that closed between 2025-11-08 and 2026-11-04, 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, 3.7% against 1.7%). Outcomes priced at 50% or more a week out happened 75% of the time (247 favourites). The overall Brier score is 0.088, but that is flattered by long shots that were clearly going to lose; on the 603 genuinely uncertain markets (priced 10–90%) it is 0.201, against 0.250 for always saying 50%.
On the 1,336 markets with a price at all three points, accuracy improves steadily as the close approaches: the Brier score is 0.087 a month before close, 0.064 a week before and 0.048 a day before (lower is better), and favorites won 65%, 82% and 82% of the time.
Among categories with at least 20 genuinely uncertain markets, Politics & Elections markets were the most accurate a week before close (Brier 0.192 on 159 markets priced 10–90%) and Economy & Fed markets the least (0.246 on 23). Some categories have only a few dozen uncertain markets, so read differences of a few hundredths as noise.
Within this sample, more trading made no clear difference: on genuinely uncertain markets (priced 10–90% a week out) the quarter with the least volume ($28.1K to $1.14M) scored 0.192 and the quarter with the most ($7.33M and up) scored 0.208. Every market here already traded at least $10,000, so this says nothing about thinly traded markets.
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