Mass Mobilization in the Modern Era: Introducing the Opposition Movements and Groups (OMG) dataset, 1789-2019

The nature and consequences of mass mobilization are core topics in the so- cial sciences. How have mass mobilization movements evolved over time? How do key characteristics of such movements, including their social composition or ideology, influence their ability to overthrow or alter political institutions? We in- troduce the Opposition Movements and Groups (OMG) dataset, which – due to its unique contents and extensive coverage – will help researchers to better address these and many other questions about mass mobilization movements. OMG in- cludes information on the stated goals, duration, size, tactics, ideology, and social and organizational composition of 1,452 mass mobilization movements, globally, from 1789-2019. We discuss OMG’s contents, construction, validity and reliability issues, and how it complements existing datasets. We showcase the data, first, by documenting several key trends in movement characteristics since the French Revolution, and, second, by shedding new light on the much-discussed relationship between nonviolent movements and democratization.