Michelle Nicholasen in The Harvard Gazette:
When Erica Chenoweth started her predoctoral fellowship at the Belfer Center for Science and International Affairs in 2006, she believed in the strategic logic of armed resistance. She had studied terrorism, civil war, and major revolutions — Russian, French, Algerian, and American — and suspected that only violent force had achieved major social and political change. But then a workshop led her to consider proving that violent resistance was more successful than the nonviolent kind. Since the question had never been addressed systematically, she and colleague Maria J. Stephan began a research project.
For the next two years, Chenoweth and Stephan collected data on all violent and nonviolent campaigns from 1900 to 2006 that resulted in the overthrow of a government or in territorial liberation. They created a data set of 323 mass actions. Chenoweth analyzed nearly 160 variables related to success criteria, participant categories, state capacity, and more. The results turned her earlier paradigm on its head — in the aggregate, nonviolent civil resistance was far more effective in producing change.
More here.