Recent years have witnessed substantial work in the legislative studies field. But what do we know about legislatures today and are there clear criteria for comparing and classifying them? This is a new review of the state of our knowledge of parliament and tackles key questions: Do legislatures matter in legislative terms, and, if so, how much? What is the extent of the legislature’s control of the legislative process. How can we classify legislatures on the basis of their relative legislative performance. Five measures of the policy power of parliaments are applied in the country/region chapters. This book was previously published as a special issue of the leading Journal of Legislative Studies.