It can be said that the concept of performance of social systems is one of the most relevant, since all social systems - from the family, through the enterprise, to the Nation state - are only interesting in obtaining as high a performance as possible. The difficulties encountered when dealing with the concept of performance have been recognized and few books until now ventured to tackle the task, mainly because of the following three big problems: the lack of a theoretical-operational model; the lack of valid data; and the lack of computer facilities. Today these obstacles have been overcome and this is the first book based on different systemic perspectives (value theory, modelling, observation and quantification) which offers the possibility of defining and working out the concept. The book should be of great interest to sociologists, political scientists, economists, organizational theorists, managers and politicians.