Book excerpt: The purpose of the book is to investigate parliaments’ capacity to oversee government activities, policies and budget legislation. By analysing the survey data that the World Bank Institute in collaboration with the Inter-Parliamentary Union collected from 120 parliaments, Pelizzo and Stapenhurst show what tools are available to parliaments worldwide, which tools are more or less common, how oversight capacity can be estimated, how oversight capacity is related to other institutional and constitutional factors. In addition to discussing the conditions under which oversight capacity is greater, the authors perform some analyses to assess the policy implications of oversight capacity. Specifically, they look at the impact of oversight capacity on the quality of democracy and on the level of good governance.