Systematic Risk
Systematic risk is the part of return that moves with common factors — you get paid for it, and you cannot dilute it by adding names in the same factor.
Definition
Systematic Risk refers to you get paid for it, and you cannot dilute it by adding names in the same factor. 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 you get paid for it, and you cannot dilute it by adding names in the same factor 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 systematic risk is saying. If you get paid for it, and you cannot dilute it by adding names in the same factor 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 Systematic Risk: what would falsify the current reading in the next window?