Ex post evaluation of economic projections validates our shared understanding of economic methodology and methods. The recent economic history of Central Arizona Project (CAP) agriculture reveals the predictive power of economic reasoning and its policy impotence within a political environment intent on obtaining its share of federally allocated water. The financial inability and unwillingness of large irrigation districts to pay for CAP water under existing federal rules produced an urban tax- and rate-payer controlled CAP decades earlier than planned. Yet irrigation districts remain a large residual buyer of CAP water under new pricing and allocation rules. Unfortunately, water markets remain an underutilized and distrusted tool in the water development game.