Why do some nations fail while others succeed? How can we compare the political capacity of a totalitarian regime to a democracy? Are democracies always more efficient? This volume answers these key questions by providing a powerful new tool for measuring governments' strengths and weaknesses. Allowing researchers to look inside countries down to the local level as well as to compare across societies and over time, the book demonstrates convincingly that political performance is the missing link in measuring power and military capability. For the theorist, political performance data helps to fill in the gaps when GDP alone does not explain the outcome of wars. For the practical policy specialist, political performance sheds a bright light on why some governments succeed and some fail, why investments disappear in one province but multiply in another, and why it is easier to promote health programs in one region but not in its neighbor. This groundbreaking book will be an essential resource for scholars, policymakers, and institutions interested in measuring the political capacities of nations and in knowing where foreign aid and investment will be most effective.