Managing complex adaptive systems (CAS) is a constant balancing act between many goals that are often in conflict with each other. Most systems need to be managed to limit resource usage i.e. they need to be efficient. The mantra of efficiency is most visible in economic systems but even other systems such as biological systems cannot typically get away with profligate wastage of resources. But efficiency is not enough. Systems also need to be robust. There is no point in achieving optimal efficiency if the first change in environmental conditions causes the system to collapse. Robustness is not just about avoiding collapse and persisting. Robustness is the ability of a system to maintain critical functionality in the face of significant stress.