INTRODUCTION
Social media in China appears as vibrant and extensive as in any Western country, with more than 1,300 social media companies and websites, and millions of posts authored every day by people all over the country. At the same time, the Chinese regime imposes extensive and varied controls over of the entire system (Brady 2009;Cairns and Carlson 2016;Knockel et al. 2015;MacKinnon 2012;Ng 2015;Shirk 2011;Stockmann 2013;Stockmann and Gallagher 2011;Yang 2009). Which social media companies are prevented from operating in China is easy to see (the so-called Great Firewall of China), and the scholarly literature now offers considerable evidence on how and why Gary King is Albert J. Weatherhead III University Professor, Institute for Quantitative Social Science, 1737 Cambridge St., Harvard University, Cambridge MA 02138; GaryKing.org (King@Harvard.edu).Jennifer Pan is Assistant Professor, Department of Communication, 450 Serra Mall, Building 120, Stanford University, Stanford CA 94304; jenpan.com (jp1@stanford.edu).Margaret E. Roberts is Assistant Professor, Department of Political Science, University of California, San Diego, Social Sciences Building 301, 9500 Gilman Dr., #0521, La Jolla, CA 92093-0521; MargaretRoberts.net (meroberts@ucsd.edu).Our thanks to Neel Guha, Peter Dyrud, Yingjie Fan, and many others for superb research assistance; Danielle Allen, Peter Bol, Becky Fair, Chase Harrison, Iain Johnston, Franziska Keller, Blake Miller, Jean Oi, Samantha Ravich, Brandon Stewart, Daniela Stockmann, Andy Walder, Yuhua Wang, Chaodan Zheng, and Yun Zhu for helpful comments; and DARPA (contract W31P4Q-13-C-0055/983-3) and the National Science Foundation (grant 1500086) for research support. Authors are listed alphabetically. Data and information necessary to replicate the results in this article appear in King et al. (2017).Received: August 26, 2016; revised: November 6, 2016; accepted: April 11, 2017. they censor certain individual social media posts that have appeared on the web or filter them out before appearing. In both cases, the censorship apparatus allows a great deal of criticism of the regime, its officials, and their policies (which can be useful information for the central government in managing local leaders) but stops discussions that can generate collective action on the ground .
1According to numerous speculations by scholars, activists, journalists, officials in other governments, and participants in social media, the Chinese regime also conducts "astroturfing," or what we might call reverse censorship, surreptitiously posting large numbers of fabricated social media comments as if they were the genuine opinions of ordinary Chinese people. The people hired for this purpose are known formally as Internet commentators ( ), although more widely as 50c party members ( ), so called because they are rumored to be paid 50 cents (5 jiao, , or about $0.08) to write and post each comment (Tong and Lei 2013). We show that this rumor turns out to be incorrect; however, we adopt this widely used ter...