Licensed emergency department (ED) capacity is a static measure that is inadequate to evaluate a system that the public and policymakers expect to respond dynamically to individual patients in a timely manner. Government mandates on hospital-based providers, undersupply of trained and willing personnel, and private market imperatives all curtail the functional capacity of the emergency care system. Although most Californians still live within a few miles of the closest hospital, many ambulance patients are diverted much further because of ED crowding. Many ambulatory patients are delayed so long in waiting rooms that they return home without ever being seen.