Chenoweth talks more about the subject here: http://w4t.pw/1x
The dataset sounds large:
I collected data on all major nonviolent and violent campaigns for the overthrow of a government or territorial liberation since 1900. The data cover the entire world and include every known campaign that consists of at least a thousand observed participants, which constitutes hundreds of cases.
How many people does it take for successful civil resistance?
Researchers used to say that no government could survive if five percent of its population mobilized against it. But our data reveal that the threshold is probably lower. In fact, no campaigns failed once they’d achieved the active and sustained participation of just 3.5% of the population—and lots of them succeeded with far less than that . Now, 3.5% is nothing to sneeze at. In the U.S. today, this means almost 11 million people.
Why Civil Resistance Works | Books | Columbia University Press
Why Civil Resistance Works – Browse and buy the Hardcover edition of Why Civil Resistance Works by , Maria J. Stephan.