"For every action in nature there is an equal and opposite reaction." - Sir Isaac Newton
The performance - or, health - of complex systems is difficult to measure. Typically, you need deviations from norms across numerous sensors - the analytics - converging to signal whether a complex system is functioning properly or not. Add the inevitability of change, and the task becomes exponentially more challenging as continuity of measurement over time decays...
And then, there's the stuff that's difficult to measure, if it's measured at all. The intangibles. The slippage factors that don't come into . . .