This book arose out of a paper that I wrote for the World Bank at the request of Ariel Dinar, the editor for the series in which this volume appears. I began that paper by pointing to the growing importance of demand-side considerations in water resources: "The provision of potable water is one of government's oldest functions with evidence of this activity stretching back thousands of years. During much of that time, water demands were taken as exogenously given and the principle task of authorities was defined as an engineering one: how to supply a given quantity of water at least cost. In...