Chaos, criticality, and public health.

Self-organized criticality offers more than a descriptive model or a doomsday forecast. We have tried to suggest that it is a paradigm for understanding the interconnections between apparently complex processes. At best, it suggests a method for finding the pressure points that can be used to bring unstable systems of public health services into greater levels of stability. The model enjoins us to understand that our goal is not to achieve equilibrium--that perfect match between the demand for health services and its delivery--but rather stability (or, more precisely, metastability). As is true of the sandpile, our systems of public health are constantly evolving. If we are correct, then the mechanism driving this ostensibly complex pattern of change and growth reflects the existence of simpler and, hopefully, more manageable processes. By monitoring these processes, it may be increasingly possible to adapt to change and even manage it effectively.