A whopping 50% of all content consumed on Twitter is generated by only 20,000 users according to this study. This is no 80/20 rule: even if we assume that a significant number of Twitter accounts are dormant (which appears to be a valid assumption), a very, very small group of “elite” users (0.05% of all users by Yahoo Research’s calculation) is producing half of the content that gets consumed.

Twitter isn’t very social: study | Econsultancy.