Modeling the Structure of Collective Action1 This material is based upon work supported by the National Science Foundation under Grant No. 0352517. The authors are equal contributors to this article.

Abstract We propose an improved theoretical approach to the rich variety of collective action now present in public life. Toward this end, we advance a conception of collective action as communicative in nature, and offer a two-dimensional model of collective action space, comprising dimensions for (a) the mode of interpersonal interaction and (b) the mode of engagement that shapes interaction. We illustrate the perspective by describing the location of a variety of contemporary collective action groups within it and by an explication of the space that reveals its utility for making sense of modern collective action efforts. Specifically, we apply the collective action space to illustrate the changing presence of collective action groups over time, deviations in collective action groups through changes in size, shape, and location, and variations in the experiences and motivations of people engaged in collective action efforts. Finally, we show how our communicative approach to collective action can integrate the insights of several theoretical traditions, including collective action theory, social capital theory, and aspects of organization theory. Keywords: Collective ActionNew TechnologyOrganizingCommunication and Information TechnologyPublic Goods The authors would like to thank Janet Fulk, Peter Monge, and Bart van den Hooff for their helpful comments on this work. Notes This material is based upon work supported by the National Science Foundation under Grant No. 0352517. The authors are equal contributors to this article. 1. Specifically, Marwell and Oliver (Citation1993; Oliver & Marwell, Citation1988) argue that when groups are heterogeneous and the public good is highly nonrival (i.e., its use by one person does not diminish its value to other users), larger interest groups can have a smaller critical mass. This is the case because large, heterogeneous groups (versus smaller, homogenous ones) contain "more total resources and larger numbers of highly interested people" (Marwell & Oliver, Citation1993, p. 46). Therefore, it is more likely in such groups that people will have more resources to contribute, thus increasing the total contributions and reaching critical mass sooner. However, if the cost of a public good increases in proportion to the number of those who benefit from it, larger groups are less likely to supply public goods, as Olson (Citation1965) argued. Most public goods with low nonrivalness (i.e., use by one person diminishes the value to others), though, are also highly excludable, and thus constitute private versus public goods. 2. The formation, maintenance, evolution, and dissolution of interorganizational relationships (IORs) complicate charting the distribution of groups over time and predicting the movement of extant groups. As Oliver (Citation1990) argues, there are several determinants of IOR formation (necessity, asymmetry, reciprocity, efficiency, stability, and legitimacy), all of which may apply to collective action organizations under the right circumstances. As one example, in the case of the Million Mom March merging with The Brady Campaign to Control Gun Violence group, these groups enjoyed a reciprocal relationship where each benefited from coalition building as a result of the merger. Thus, the formation of IORs can alter a group's location and degree of variation in both the mode of interaction and the mode of engagement, in many cases quickly and radically. Moreover, depending on the nature of the IOR, such alterations may be short term (e.g., a strategic alliance) or long term (e.g., a federation). Additional informationNotes on contributorsAndrew J. Flanagin Andrew J. Flanagin (Ph.D., Annenberg School for Communication, University of Southern California) is an associate professor in the Department of Communication at the University of California, Santa Barbara Cynthia Stohl Cynthia Stohl (Ph.D., Purdue University) is a professor in the Department of Communication at the University of California, Santa Barbara Bruce Bimber Bruce Bimber (Ph.D., Massachusetts Institute of Technology) is a professor in the Departments of Political Science and Communication at the University of California, Santa Barbara