Homophily, Group Size, and the Diffusion of Political Information in Social Networks: Evidence from Twitter

Yosh Halberstam, Brian Knight

NBER Working Paper No. 20681
Issued in November 2014
NBER Program(s):Public Economics, Political Economy

In this paper, we investigate political communications in social networks characterized both by homophily–a tendency to associate with similar individuals–and group size. To generate testable hypotheses, we develop a simple theory of information diffusion in social networks with homophily and two groups: conservatives and liberals. The model predicts that, with homophily, members of the majority group have more network connections and are exposed to more information than the minority group. We also use the model to show that, with homophily and a tendency to produce like-minded information, groups are disproportionately exposed to like-minded information and the information reaches like-minded individuals more quickly than it reaches individuals of opposing ideologies. To test the hypotheses of our model, we analyze nearly 500,000 communications during the 2012 US elections in a social network of 2.2 million politically-engaged Twitter users. Consistent with the model, we find that members of the majority group in each state-level network have more connections and are exposed to more tweets than members of the minority group. Likewise, we find that groups are disproportionately exposed to like-minded information and that information reaches like-minded users more quickly than users of the opposing ideology.

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Document Object Identifier (DOI): 10.3386/w20681

Published: Yosh Halberstam & Brian Knight, 2016. "Homophily, group size, and the diffusion of political information in social networks: Evidence from Twitter," Journal of Public Economics, . citation courtesy of

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