Flat staking is comfortable. Every bet is the same size, the maths is trivial, and a losing streak feels survivable. Kelly is uncomfortable — bets vary, big edges sting on losses, and the formula tells you to do things your gut won't. The 2024 NRL backtest is a fair fight between the two, run on the same picks the Edgewise NRL ensemble actually produced.
The setup
Same 384 picks across H2H and Line markets, edge filter ≥ 3 pp, starting bankroll $10,000. Both plans bet only when the scanner flagged an edge — no martingale, no doubling-up, no skipping picks based on feel.
Result — final bankrolls
Kelly produced nearly 2× the return — at almost 2× the drawdown. That trade-off is not free, and it's the central question of any staking plan.
What's actually happening
Flat staking
A 1-unit flat bet is, mathematically, a constant fraction of the starting bankroll. As the bankroll grows, your effective stake-as-percent shrinks, and you under-bet your edge. The flat plan ended the season risking roughly 0.85% per pick, even though it could have safely risked more.
¼ Kelly
Kelly recalculates after every settled bet, so the stake-as-percent stays roughly constant in compound terms. When you're winning, you press; when you're losing, you reduce. The result is exponential rather than linear growth — at the cost of deeper drawdowns when a cold patch hits.
Why not full Kelly
Full Kelly is theoretically optimal when your true probabilities are known with certainty. They're not. Sports models have estimation error, and full Kelly punishes that error brutally — a 5 pp model overestimate at full Kelly can wipe out 20–30% of a bankroll in a single bad week. Fractional Kelly (¼ or ⅓) keeps most of the geometric-growth benefit while dampening the variance you actually face.
The pitfall flat hides
Flat staking looks safer because the numbers feel steady, but it's actively wasting edge. Over 384 picks with a real 4.6 pp average edge, the flat plan left roughly $1,630 on the table — purely from under-betting. That gap compounds. Across three seasons, the same picks under flat vs ¼ Kelly produce a ~60% bankroll gap.
How to run this yourself
Open Backtest → Sport = NRL → choose any NRL model → Strategy Comparison tab. Set strategy A to flat 1% and strategy B to ¼ Kelly with the same edge filter. The engine will produce the same side-by-side curves you see in this post on your own bankroll size and risk preferences.