Varieties of Democracy has set a new gold standard for studying political regimes: by establishing the conceptual underpinnings of new measures of a range of attributes of political democracy; for its cutting-edge methodological sophistication; for contributing a data set unmatched in the scope and variety of its coverage across time and space. Amongst many other contributions: creating a new index of electoral democracy alongside four additional theoretically grounded indices of democracy based on liberal, participatory, deliberative, and egalitarian traditions; uniquely integrating qualitative and quantitative measures along dozens of dimensions of political regimes based upon some 450 different indicators. This book explains the logic and methods related to data collection, measurement, reliability, and validity assessment (particularly pertinent given the heavy reliance upon online surveys by country experts) with a degree of clarity that enables this book to serve as a reference for how to implement the science of the study of social phenomena. The measurement of the five key principles of democracy (with respective component indices) is explained meticulously, including the use of Bayesian factor analysis and instructive explanations of the manners in which the respective components are aggregated. One learns not merely how the V-Dem components are conceptualized and created; one 'watches' the expert application of advanced methods work its magic and comes to understand the logic underpinning it. I recommend the inclusion of Varieties of Democracy in any upper-level BA and MA course on research design and methods due to its invaluable service of revealing the thinking that lies behind the application of such methods.