The primary factor behind skilled forecasters struggling in prediction markets is seldom inaccurate forecasting — it's inadequate capital preservation. An astute probability assessment becomes worthless if a prolonged losing run depletes your entire stake. This guide outlines the methodology that safeguards against such catastrophe.
The Kelly Criterion: The Mathematical Foundation
The Kelly Criterion determines the theoretically ideal proportion of your capital to allocate to each wager: 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 delivers mathematical optimality 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 periods of underperformance occur even amongst traders with genuine advantage. Following a 20% decline in capital, scale back your position sizes by half until you restore your account to its previous peak. This approach ensures that unfavourable variance does not spiral into irreversible losses.
FAQ
- How much starting capital do I need for serious prediction market trading?
- $500-1,000 furnishes adequate reserves to construct a diversified portfolio spanning 10-20 positions using half-Kelly allocation. Amounts below $100 impose such tight constraints on individual position sizing that systematic methodology becomes impractical.
- What should I do after a winning streak?
- Exercise greater caution, not complacency. Consecutive wins breed confidence bias. Maintain adherence to your disciplined sizing protocol irrespective of current trajectory.