document: Who says what to whom on twitter We study several longstanding questions in media communications research , in the context of the microblogging service Twitter , regarding the production , flow , and consumption of information . To do so , we exploit a recently introduced feature of Twitter known as `` lists '' to distinguish between elite users - by which we mean celebrities , bloggers , and representatives of media outlets and other formal organizations - and ordinary users . Based on this classification , we find a striking concentration of attention on Twitter , in that roughly 50 % of URLs consumed are generated by just 20K elite users , where the media produces the most information , but celebrities are the most followed . We also find significant homophily within categories : celebrities listen to celebrities , while bloggers listen to bloggers etc ; however , bloggers in general rebroadcast more information than the other categories . Next we re-examine the classical `` two-step flow '' theory of communications , finding considerable support for it on Twitter . Third , we find that URLs broadcast by different categories of users or containing different types of content exhibit systematically different lifespans . And finally , we examine the attention paid by the different user categories to different news topics .
doc_bio_tags: O O O O O O B O O O O O O O B O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O