This book provides a detailed and comprehensive evaluation of water reform and water sector performance from the perspectives of institutional economics and political economy. It integrates institutional theory with resource economics, and set against an exhaustive review of the theoretical and empirical literature, the authors develop an alternative methodology to quantitatively assess the performance of institutions in the context of water. This methodology is built on the principle of 'institutional ecology', the 'institutional decomposition and analysis' framework, and the 'subjective theory' of institutional change. Using this new methodology, plus information collected through an international survey of 127 water experts, the authors present a detailed empirical analysis of the process of institution-performance interaction in the water sector. Relying on the institutional transaction cost approach and an extensive cross-country review of recent water sector reforms, they also provide evidence on the relative role of various factors that influence the extent and depth of water institutional reforms in 43 countries and regions around the world. The book concludes with far reaching implications for the theory and policy of water sector reform in particular and institutional reform in general.