“…It is commonly accepted that firms' performance is influenced not only by the skills of their managers in organising production activities, but also by a set of variables that are beyond the control of firms' managers, such as the characteristics of the environment in which production takes place or the impact of luck, be it good or bad. In the provision of water services, the nature of technical interactions between inputs and outputs is strongly conditioned by the environments in which water utilities operate (Burns, Jenkins, & Riechmann, 2005;Fabbri & Fraquelli, 2000), and the heterogeneity of these operating environments presents a major difficulty in assessing relative levels of performance. This difficulty becomes even greater when, instead of an overall measure of technical efficiency, input-specific scores are computed.…”