The Varieties of Democracy project (V-Dem) pioneered new ways to conceptualize and measure democracy, producing a multidimensional and disaggregated data set on democracy around the world that is now widely used by researchers, activists, and governments. Why Democracies Develop and Decline draws on this data to present a comprehensive overview and rigorous empirical tests of the factors that contribute to democratization and democratic decline, looking at economic, social, institutional, geographic, and international factors. It is the most authoritative and encompassing empirical analysis of the causes of democratization and reversals. The volume also proposes a comprehensive theoretical framework and presents an up-to-date description of global democratic developments from the French Revolution to the present. Each chapter leverages the specialized expertise of its authors, yet their sustained collaboration lends the book an unusually unified approach and a coherent theory and narrative.