Jane Street pays traders $400k to achieve this
Top quant experts at Polymarket use the same method
Immediately stop trading when calibration fails
**Brier Score** can accurately tell you when to stop.
Formula: \bm{\sum (\text{predicted\_probability} - \text{actual\_outcome})^2}
• Perfect prediction = 0.00
• Random blind guessing = 0.25
Why Wall Street values it so much
• Citadel tests this in interviews.
• Top traders at Polymarket self-check every 50 trades.
Even if you have a 70% win rate, your probability calibration can still be terrible.
For example:
You claim to have 90% confidence in 10 trades.
If you only win 6 in the end, you were overconfident.
Your so-called 90% confidence is actually only 60%.
The Brier Score will immediately expose this illusion.
Discipline of top experts
• Quant firms will fire traders who cannot calibrate probabilities.
• The same goes for the top 20 traders at Polymarket: they track the deviation of predicted probabilities from actual outcomes.
• When the Brier Score starts to rise, they will stop trading.
This is not out of fear, but because math tells them: your edge has disappeared.
The dividing line between amateurs and professionals
Imagine this: you made $5000 in a week, but your Brier Score jumped from 0.12 to 0.19.
• Quant experts: decisively exit.
• Amateur retail traders: continue trading and lose back all their earnings.
Why do most traders ignore this?
Because tracking the Brier Score feels like doing extra homework. You might think, "Whether I win or lose, don't I have a sense of it?"
Wrong.
• Calibration is poor but you won: it means you were just lucky.
• Calibration is good but you lost: it means you were just unlucky.
Only the Brier Score can tell you the truth.
The real moat
Trading is not about "predicting correctly," but about **"knowing when you predicted incorrectly."**
The moment your prediction no longer matches reality, you should stop betting. Quant experts have established a system that measures not only profit but also their own accuracy. #预测市场
Top quant experts at Polymarket use the same method
Immediately stop trading when calibration fails
**Brier Score** can accurately tell you when to stop.
Formula: \bm{\sum (\text{predicted\_probability} - \text{actual\_outcome})^2}
• Perfect prediction = 0.00
• Random blind guessing = 0.25
Why Wall Street values it so much
• Citadel tests this in interviews.
• Top traders at Polymarket self-check every 50 trades.
Even if you have a 70% win rate, your probability calibration can still be terrible.
For example:
You claim to have 90% confidence in 10 trades.
If you only win 6 in the end, you were overconfident.
Your so-called 90% confidence is actually only 60%.
The Brier Score will immediately expose this illusion.
Discipline of top experts
• Quant firms will fire traders who cannot calibrate probabilities.
• The same goes for the top 20 traders at Polymarket: they track the deviation of predicted probabilities from actual outcomes.
• When the Brier Score starts to rise, they will stop trading.
This is not out of fear, but because math tells them: your edge has disappeared.
The dividing line between amateurs and professionals
Imagine this: you made $5000 in a week, but your Brier Score jumped from 0.12 to 0.19.
• Quant experts: decisively exit.
• Amateur retail traders: continue trading and lose back all their earnings.
Why do most traders ignore this?
Because tracking the Brier Score feels like doing extra homework. You might think, "Whether I win or lose, don't I have a sense of it?"
Wrong.
• Calibration is poor but you won: it means you were just lucky.
• Calibration is good but you lost: it means you were just unlucky.
Only the Brier Score can tell you the truth.
The real moat
Trading is not about "predicting correctly," but about **"knowing when you predicted incorrectly."**
The moment your prediction no longer matches reality, you should stop betting. Quant experts have established a system that measures not only profit but also their own accuracy. #预测市场
