Kelly Criterion
Kelly is the stake that maximizes the expected log of wealth — an aggressive sizing rule that needs a true edge and a stomach.
Definition
Kelly Criterion refers to an aggressive sizing rule that needs a true edge and a stomach. Keep that definition fixed when comparing series, managers, or regimes — renaming the same tape does not create a new signal.
Why it matters
It shows up in factor research, attribution, and capacity debates — whether a return slice is skill, style, or fee drag. When an aggressive sizing rule that needs a true edge and a stomach shifts, related hedges, limits, and narratives usually need an explicit update rather than a quiet assumption.
Case
Suppose a desk is positioned for the opposite of what kelly criterion is saying. If an aggressive sizing rule that needs a true edge and a stomach moves against that book, the first question is not “is the story clever?” but whether size, hedges, and stop logic still match the observation.
How to read it
Check definition stability across universes, costs, and regimes before treating a backtest as portable. Prefer a short written null hypothesis for Kelly Criterion: what would falsify the current reading in the next window?