2.1%
Average Pinnacle margin — the tightest market available. Your edge must exceed this.
500+
Minimum bets before ROI data carries statistical significance.
3–8%
Realistic ROI range for professional value bettors over large samples.
87%
Of long-term losses attributable to psychology and staking errors — not model failure.
Market structure
Bookmaker margins by operator
The margin embedded in odds varies significantly between operators. Betting into a 10% margin market requires a substantial edge just to break even.
| Operator | Avg. Margin | Sharp-Friendly | Limits |
|---|---|---|---|
| Pinnacle | 2.1% | Yes | High |
| Betfair Exchange | 2.5% | Yes | Market depth |
| Bet365 | 5.6% | No | Low (sharps) |
| Unibet | 6.8% | No | Low |
| William Hill | 8.4% | No | Very low |
Bankroll management
Kelly Criterion — by the numbers
Given a 5% edge on an even-money bet, fractional Kelly (25%) suggests staking 1.25% of bankroll per bet.
Kelly % = (bp − q) / b — where b = odds−1, p = win prob, q = 1−p
| Edge | Odds | Full Kelly | Quarter Kelly |
|---|---|---|---|
| 2% | 2.00 | 2.0% | 0.5% |
| 5% | 2.00 | 5.0% | 1.25% |
| 5% | 3.00 | 2.5% | 0.63% |
| 10% | 2.00 | 10.0% | 2.5% |
Variance
Losing runs — even with edge
Even with a genuine 5% edge, a losing run of 14+ bets occurs roughly once every 100 bets at even money. At longer odds, worse drawdowns are statistically guaranteed.
| Edge | Odds | Expected losing run (1-in-100) |
|---|---|---|
| 5% | 2.00 | 14 bets |
| 5% | 3.00 | 22 bets |
| 5% | 5.00 | 36 bets |
| 3% | 2.00 | 18 bets |