Prediction Market Bankroll Management: Never Blow Up Your Account

The most common reason skilled forecasters struggle on prediction markets isn't inaccurate forecasting — it's inadequate bankroll discipline. Even an excellent probability assessment becomes worthless if a run of losses eliminates your capital. This guide outlines the methodology that safeguards against catastrophic loss.

The Kelly Criterion: The Mathematical Foundation

Kelly Criterion determines the theoretically ideal proportion of your bankroll to deploy on each trade: f = (bp - q) / b

• b = net odds received (e.g., if YES costs 0.40, b = 1.5)
• p = your probability estimate
• q = 1 - p
• Result: optimal fraction of bankroll for this position

In practice: use half-Kelly. Whilst Kelly maximises returns under certainty, our probability assessments carry inherent uncertainty, making half-Kelly the superior choice for risk-adjusted performance.

Hard Rules: Never Break These

• Maximum 5% of bankroll per single position — no exceptions regardless of conviction
• Maximum 25% of bankroll in any single correlated cluster — e.g., all US election markets
• Stop-loss: if you lose 25% of your starting bankroll in a month, stop trading for the rest of the month
• Never add to a losing position to "average down" — reevaluate the fundamental thesis first

Drawdown Recovery

Inevitable downturns occur even amongst traders with genuine edge. Following a 20% drawdown, cut your position sizes in half until you climb back to your previous peak. This approach ensures that unfavourable periods don't spiral into account destruction.

FAQ

How much starting capital do I need for serious prediction market trading?

£350–700 (approximately $500-1,000) allows sufficient diversification across 10-20 positions using half-Kelly allocation. Amounts below £70 (approximately $100) create sizing constraints that undermine systematic methodology.

What should I do after a winning streak?

Increase critical scrutiny rather than confidence. Consecutive wins breed complacency. Maintain your disciplined sizing framework independent of short-term results.