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***** To join INSNA, visit http://www.insna.org ***** Dear All, Several on this list may be interesting in this paper we just published in PNAS. It develops a method for distinguishing peer influence from homophily in large dynamic networks. We apply it to 27 million users of Yahoo's instant messaging graph to predict influence in the adoption of a new mobile service application. Enjoy:) http://www.pnas.org/content/106/51/21544.short "Distinguishing Influence Based Contagion from Homophily Driven Diffusion in Dynamic Networks" ABSTRACT: Node characteristics and behaviors are often correlated with the structure of social networks over time. While evidence of this type of assortative mixing and temporal clustering of behaviors among linked nodes is used to support claims of peer influence and social contagion in networks, homophily may also explain such evidence. Here we develop a dynamic matched sample estimation framework to distinguish influence and homophily effects in dynamic networks, and we apply this framework to a global instant messaging network of 27.4 million users, using data on the day-by-day adoption of a mobile service application and users’ longitudinal behavioral, demographic, and geographic data. We find that previous methods overestimate peer influence in product adoption decisions in this network by 300–700%, and that homophily explains 50% of the perceived behavioral contagion. These findings and methods are essential to both our understanding of the mechanisms that drive contagions in networks and our knowledge of how to propagate or combat them in domains as diverse as epidemiology, marketing, development economics, and public health. -- Sinan Aral Assistant Professor, NYU Stern School of Business. Research Affiliate, MIT Sloan School of Management. Personal Webpage: http://pages.stern.nyu.edu/~saral SSRN Page: http://ssrn.com/author=110270 WIN Workshop: http://www.winworkshop.net _____________________________________________________________________ SOCNET is a service of INSNA, the professional association for social network researchers (http://www.insna.org). To unsubscribe, send an email message to [log in to unmask] containing the line UNSUBSCRIBE SOCNET in the body of the message.