Since the 1990s, efficiency and benchmarking analysis has increasingly been used in network utilities research and regulation. A recurrent concern is the effect of environmental factors that are beyond the influence of firms (observable heterogeneity) and factors that are not identifiable...

Quality of service is of major economic significance in natural monopoly infrastructure industries and is increasingly addressed in regulatory schemes. However, this important aspect is generally not reflected in efficiency analysis of these industries. In this paper we present an efficiency...