How accurate are prediction markets?

In August 2026, 65% of the 26 highest-volume Polymarket markets resolved to the outcome that was priced above 50% a day before close, with a Brier score of 0.173.

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: August 2026

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 01:56 UTC · Source: Polymarket · 18+

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

Favorites that won

65%

17 of 26 markets where the eventual result was priced above 50% a day before

Brier score (1 day out)

0.173

0 is perfect, 0.25 is a coin flip

Markets graded

highest-volume resolutions, August 2026

Resolved markets, August 2026

Market	Result	1 day before	7 days before	Volume
Dota 2: TEAM VISION vs Team Spirit (BO5) - The International Playoffs resolved August 23, 2026	Team Spirit	–	–	$25.1M
What price will Bitcoin hit in July? resolved July 14, 2026	↑ 65,000	54.5%	77.5%	$25.0M
What will WTI Crude Oil (WTI) hit in July 2026? resolved July 23, 2026	↑ $90	71.3%	22.4%	$17.8M
US x Iran Effective Ceasefire by...? (2 week pause) resolved August 12, 2026	July 31	93.5%	83.5%	$17.2M
Aston Villa FC vs. Arsenal FC resolved August 31, 2026	Arsenal FC	63.5%	63.5%	$12.3M
Dota 2: TEAM VISION vs Team Yandex (BO3) - The International Playoffs resolved August 22, 2026	TEAM VISION	–	–	$11.8M
Dota 2: Team Spirit vs TEAM VISION (BO3) - The International Playoffs resolved August 21, 2026	TEAM VISION	61.0%	–	$11.3M
Dota 2: Team Liquid vs Team Falcons (BO3) - The International Playoffs resolved August 21, 2026	Team Falcons	–	–	$11.2M
Dota 2: Nigma Galaxy vs Team Falcons (BO3) - The International Playoffs resolved August 20, 2026	Team Falcons	62.5%	–	$11.2M
Dota 2: Iron Wing vs BoomBoys (BO3) - The International Playoffs resolved August 21, 2026	Iron Wing	–	–	$11.0M
Counter-Strike: Team Falcons vs Lynn Vision (BO3) - BLAST Open Porto Group B resolved August 27, 2026	Team Falcons	76.5%	48.5%	$10.9M
Dota 2: Team Yandex vs Team Spirit (BO3) - The International Playoffs resolved August 23, 2026	Team Spirit	–	–	$10.5M
Counter-Strike: FURIA vs FUT Esports (BO3) - Esports World Cup Playoffs resolved August 22, 2026	FUT Esports	42.5%	–	$9.9M
Florida Governor Republican Primary Winner resolved August 19, 2026	Byron Donalds	99.1%	98.6%	$9.8M
Dota 2: Team Yandex vs Nigma Galaxy (BO3) - The International Playoffs resolved August 21, 2026	Nigma Galaxy	–	–	$9.5M
Dota 2: Team Spirit vs Team Liquid (BO3) - The International Playoffs resolved August 22, 2026	Team Spirit	–	–	$9.5M
Dota 2: TEAM VISION vs BoomBoys (BO3) - The International Playoffs resolved August 20, 2026	TEAM VISION	64.5%	–	$9.4M
LoL: KT Rolster vs HANJIN BRION (BO5) - LCK Play-In resolved August 26, 2026	KT Rolster	67.0%	–	$8.5M
LoL: T1 vs BNK FEARX (BO5) - LCK Playoffs resolved August 29, 2026	T1	–	–	$8.3M
Dota 2: Team Liquid vs Team Yandex (BO3) - The International Playoffs resolved August 20, 2026	Team Yandex	46.5%	–	$8.3M
LoL: Top Esports vs LGD Gaming (BO5) - LPL Playoffs resolved August 29, 2026	LGD Gaming	38.5%	–	$7.8M
Counter-Strike: Legacy vs FUT Esports (BO3) - BLAST Open Porto Group B resolved August 27, 2026	Legacy	44.5%	48.0%	$7.2M
LoL: HANJIN BRION vs BNK FEARX (BO5) - LCK Play-In resolved August 28, 2026	BNK FEARX	–	–	$7.1M
Counter-Strike: Spirit vs MOUZ (BO5) - BLAST Bounty Playoffs resolved August 2, 2026	MOUZ	–	–	$7.0M
Dota 2: Team Falcons vs Team Liquid (BO5) - 1win Essence Playoffs resolved August 5, 2026	Team Liquid	–	–	$6.9M
LoL: Nongshim Red Force vs BNK FEARX (BO5) - LCK Play-In resolved August 27, 2026	Nongshim Red Force	55.5%	–	$6.9M
Counter-Strike: FUT Esports vs Spirit (BO5) - Esports World Cup Playoffs resolved August 23, 2026	FUT Esports	–	–	$6.7M
Dota 2: BoomBoys vs Team Spirit (BO3) - The International Playoffs resolved August 22, 2026	Team Spirit	–	–	$6.7M
Counter-Strike: Vitality vs Spirit (BO3) - Esports World Cup Playoffs resolved August 21, 2026	Spirit	43.5%	–	$6.6M
Real Madrid CF vs. Real Sociedad de Fútbol resolved August 26, 2026	Real Madrid CF	74.5%	70.5%	$6.6M
LoL: JD Gaming vs Team WE (BO5) - LPL Playoffs resolved August 30, 2026	Team WE	40.0%	–	$6.6M
Chelsea FC vs. Brighton & Hove Albion FC resolved August 30, 2026	Chelsea FC	53.5%	48.5%	$6.5M
UFC 330: Islam Makhachev vs. Ian Machado Garry (Welterweight, Main Card) resolved August 16, 2026	Islam Makhachev	75.5%	75.5%	$6.4M
Where will Maxx Crosby play in 2026? resolved September 1, 2026	Las Vegas Raiders	94.5%	95.1%	$6.4M
LoL: DN SOOPers vs Kiwoom DRX (BO3) - KeSPA Cup Last Chance Qualifier resolved August 10, 2026	Kiwoom DRX	67.0%	–	$6.4M
LoL: T1 vs DN SOOPers (BO5) - KeSPA Cup Playoffs resolved August 17, 2026	T1	46.5%	–	$6.3M
Counter-Strike: G2 vs FURIA (BO3) - Esports World Cup Playoffs resolved August 20, 2026	FURIA	–	–	$6.2M
What price will Ethereum hit in July? resolved July 15, 2026	↑ 1,900	83.0%	45.5%	$6.2M
LoL: T1 vs Hanwha Life Esports (BO3) - LCK Round 3-4 Legend Group resolved August 8, 2026	T1	48.5%	–	$6.1M
LoL: Hanwha Life Esports vs Gen.G (BO3) - LCK Round 3-4 Legend Group resolved August 5, 2026	Gen.G	47.5%	–	$6.0M

"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 August 2026, 65% of the 26 highest-volume Polymarket markets resolved to the outcome that was priced above 50% a day before close, with a Brier score of 0.173.
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.