How accurate are prediction markets?

In the last 30 days, 66% of the 35 highest-volume Polymarket markets resolved to the outcome that was priced above 50% a day before close, with a Brier score of 0.214.

What is a Brier score?

The average squared difference between the forecast probability and the outcome (1 if it happened, 0 if not). Lower is better; a constant 50% forecast scores 0.25.

Which markets are included?

Resolved Polymarket events with more than $50K of volume in the selected window, up to 40 per month, graded on the price one day and one week before close.

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Resolved markets

Prediction market scorecard: the last 30 days

For every high-volume market that resolved, we record what Polymarket priced the eventual outcome at one day and one week before close. This is the record, good and bad.

Updated 2026-11-06 01:33 UTC · Source: Polymarket · 18+

Last 30 days Nov 2026 Oct 2026 Sep 2026 Aug 2026 Jul 2026 Jun 2026

Favorites that won

66%

23 of 35 markets where the eventual result was priced above 50% a day before

Brier score (1 day out)

0.214

0 is perfect, 0.25 is a coin flip

Markets graded

highest-volume resolutions, the last 30 days

Resolved markets, the last 30 days

Market	Result	1 day before	7 days before	Volume
Brazil Presidential Election resolved October 26, 2026	Luiz Inácio Lula da Silva	21.5%	21.5%	$249.1M
Fed Decision in October? resolved October 28, 2026	No change	94.5%	87.5%	$101.9M
Balance of Power: 2026 Midterms resolved November 4, 2026	Democrats Sweep	75.5%	66.5%	$75.7M
Which coalition will form the next Dutch government? resolved February 23, 2026	VVD + CDA + D66	99.8%	99.4%	$70.4M
Who will be confirmed as Fed Chair? resolved May 14, 2026	Kevin Warsh	100.0%	99.7%	$64.5M
Which party will win the House in 2026? resolved November 4, 2026	Democratic Party	94.5%	91.5%	$63.3M
MLB World Series Champion 2026 resolved October 29, 2026	Milwaukee Brewers	91.6%	63.1%	$48.2M
NBA: LeBron James Next Team resolved July 27, 2026	Philadelphia 76ers	99.7%	8.5%	$46.2M
California Governor Election Winner resolved November 4, 2026	Xavier Becerra	98.2%	96.7%	$44.9M
Which party will win the Senate in 2026? resolved November 4, 2026	Democratic Party	76.5%	66.5%	$31.5M
2026 Men’s US Open Winner (Tennis) resolved September 14, 2026	Alexander Zverev	57.9%	21.6%	$26.4M
Texas Senate Election Winner resolved November 4, 2026	James Talarico (D)	74.5%	67.5%	$21.8M
What price will Bitcoin hit in October? resolved October 1, 2026	↑ 85,000	–	–	$17.4M
Israeli Legislative Election Winner resolved October 31, 2026	Likud	99.4%	30.5%	$17.0M
LoL: Top Esports vs Invictus Gaming (BO5) - Worlds Playoffs resolved November 4, 2026	Invictus Gaming	51.5%	–	$15.9M
Nottingham Forest FC vs. Arsenal FC resolved October 18, 2026	Arsenal FC	59.5%	62.5%	$13.7M
Michigan Senate Election Winner resolved November 4, 2026	Abdul El-Sayed (D)	80.5%	69.5%	$13.7M
LoL: Gen.G vs LYON (BO5) - Worlds Playoffs resolved November 5, 2026	Gen.G	81.5%	–	$13.6M
Serbia Parliamentary Election Winner resolved October 26, 2026	Student List – Students Win	28.0%	31.5%	$11.3M
Cavaliers vs. 76ers resolved October 23, 2026	76ers	57.5%	59.0%	$11.2M
AS Roma vs. Real Madrid CF resolved October 14, 2026	Real Madrid CF	48.5%	51.5%	$11.1M
LoL: Team Liquid vs LOS (BO3) - Worlds Group Stage resolved October 30, 2026	LOS	28.5%	–	$10.9M
FC Barcelona vs. Real Madrid CF resolved October 25, 2026	Real Madrid CF	25.5%	20.5%	$10.8M
Bills vs. Rams resolved October 13, 2026	Bills	38.5%	40.5%	$10.7M
LoL: FURIA Esports vs Cloud9 (BO5) - Worlds Play-In resolved October 17, 2026	Cloud9	–	–	$10.5M
Brazil Presidential Election Second Round: Margin of Victory resolved October 26, 2026	Lula da Silva <4%	18.5%	20.5%	$10.3M
LoL: Cloud9 vs Karmine Corp (BO5) - Worlds Play-In resolved October 15, 2026	Cloud9	40.5%	–	$10.1M
Trail Blazers vs. Lakers resolved October 28, 2026	Trail Blazers	43.5%	–	$10.1M
Commanders vs. 49ers resolved October 20, 2026	49ers	78.5%	77.5%	$10.1M
Chiefs vs. Seahawks resolved October 26, 2026	Seahawks	58.5%	55.0%	$9.8M
LoL: LOS vs LYON (BO3) - Worlds Group Stage resolved October 31, 2026	LOS	–	–	$9.6M
Chelsea FC vs. Tottenham Hotspur FC resolved October 24, 2026	Tottenham Hotspur FC	23.5%	23.0%	$9.4M
Ravens vs. Falcons resolved October 12, 2026	Ravens	38.5%	65.0%	$9.4M
76ers vs. Knicks resolved October 21, 2026	76ers	38.5%	35.0%	$9.2M
76ers vs. Hornets resolved November 1, 2026	76ers	51.5%	–	$9.2M
LoL: Invictus Gaming vs LYON (BO3) - Worlds Group Stage resolved October 29, 2026	Invictus Gaming	59.5%	–	$9.2M
Dota 2: Team Yandex vs Team Spirit (BO5) - BLAST Slam Playoffs resolved October 11, 2026	Team Spirit	–	–	$9.1M
LoL: Gen.G vs LYON (BO3) - Worlds Group Stage resolved October 25, 2026	LYON	–	–	$9.0M
Club Atlético de Madrid vs. Manchester United FC resolved October 13, 2026	Club Atlético de Madrid	50.5%	44.5%	$8.8M
Eagles vs. Commanders resolved November 2, 2026	Commanders	70.5%	64.0%	$8.8M

"1 day before" is the Polymarket price of the outcome that eventually happened, 24 hours before the market was closed for resolution. Brier score averages (1 - price)² over graded markets.

How to read the scorecard

Calibration, not hit rate, is the real test: a market is doing its job if outcomes priced at 70% happen about 70% of the time, which means favorites should lose roughly 30% of the time at that price. A Brier score near 0.1 across a month is strong; 0.25 is no better than a coin flip. Sample sizes here are small, so treat one month as a snapshot. Methodology and the full court and enforcement data live in the tracker and editorial standards.

Frequently asked questions

How accurate are prediction markets?: In the last 30 days, 66% of the 35 highest-volume Polymarket markets resolved to the outcome that was priced above 50% a day before close, with a Brier score of 0.214.
What is a Brier score?: The average squared difference between the forecast probability and the outcome (1 if it happened, 0 if not). Lower is better; a constant 50% forecast scores 0.25.
Which markets are included?: Resolved Polymarket events with more than $50K of volume in the selected window, up to 40 per month, graded on the price one day and one week before close.