For the purposes of this article, we refer to two nurse staff allocation methods used in various forms in some hospitals in Australia and New Zealand: nurse patient ratios (NPRs) and computerized nurse dependency workload systems. Generally, computerized nurse dependency workload systems incorporate the dimension of patient acuity. The terms patient acuity, nurse dependency, and patient dependency refer to similar phenomenon where patient needs for nursing care are described and/or measured. In some Australian health services, NPRs are part of a formalized system. In other health services, nurse-patient ratios have been adapted by hospital managers internally as a model for setting safe staff levels external to formalized structures.