Measuring Media Diversity Online and Oine: Evidence from Political Websites

Abstract As policymakers and scholars debate the impact of the Web on democratic discourse, one crucial question has remained unanswered: out of the millions of politically-relevant sites online, how many do citizens actually use? To gather evidence on this question, we examine the link structure surrounding political Web- sites. We show that the number of hyperlinks a site receives is highly correlated with site trac and is a key determinant of search engine ranking. In the,rst large-scale survey of online politi- cal content, we download and classify millions of Web pages. Links within political communities follow highly-concentrated power law distributions focused on a few hyper-successful sites. The level of concentration we,nd in links and site trac|both,overall and within political communities|is comparable to or even greater than that found in traditional media. This fact challenges much of the conventional wisdom about the Internet’s inuence,on political life. We gratefully acknowledge the contributions of Lada Adamic, Larry Bartels, Adam Berinsky, Kenneth Cukier, Paul DiMaggio, Eszter Hargittai, Jennifer Hochschild, Chris Karpowitz, Gabriel Lenz, Arthur Lupia, Christopher J. Mackie, Eli Noam, Clay Shirky, and Adam Simon. Any errors are our own. Research Sta Member, NEC Laboratories America (4 Independence Way, Princeton, NJ 08540; jaj@nec-labs.com) 1