document: What is Twitter , a social network or a news media ? Twitter , a microblogging service less than three years old , commands more than 41 million users as of July 2009 and is growing fast . Twitter users tweet about any topic within the 140-character limit and follow others to receive their tweets . The goal of this paper is to study the topological characteristics of Twitter and its power as a new medium of information sharing . We have crawled the entire Twitter site and obtained 41.7 million user profiles , 1.47 billion social relations , 4,262 trending topics , and 106 million tweets . In its follower-following topology analysis we have found a non-power-law follower distribution , a short effective diameter , and low reciprocity , which all mark a deviation from known characteristics of human social networks ( 28 ) . In order to identify influentials on Twitter , we have ranked users by the number of followers and by PageRank and found two rankings to be similar . Ranking by retweets differs from the previous two rankings , indicating a gap in influence inferred from the number of followers and that from the popularity of one 's tweets . We have analyzed the tweets of top trending topics and reported on their temporal behavior and user participation . We have classified the trending topics based on the active period and the tweets and show that the majority ( over 85 % ) of topics are headline news or persistent news in nature . A closer look at retweets reveals that any retweeted tweet is to reach an average of 1,000 users no matter what the number of followers is of the original tweet . Once retweeted , a tweet gets retweeted almost instantly on next hops , signifying fast diffusion of information after the 1st retweet . To the best of our knowledge this work is the first quantitative study on the entire Twittersphere and information diffusion on it .
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