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Recently, Twitter has emerged as a popular platform for discovering real-time information on the Web, such as news stories and people's reaction to them. Like the Web, Twitter has become a target for link farming, where users, especially spammers, try to acquire large numbers of follower links in the social network. Acquiring followers not only increases(More)
Geography plays an important role in shaping societal interactions in the offline world. However, as more and more social interactions occur online via social networking sites like Twitter and Facebook, users can interact with others unconstrained by their geolocations, raising the question: does offline geography still matter in online social networks? In(More)
Feld's friendship paradox states that " your friends have more friends than you, on average. " This paradox arises because extremely popular people, despite being rare, are overrepre-sented when averaging over friends. Using a sample of the Twitter firehose, we confirm that the friendship paradox holds for >98% of Twitter users. Because of the directed(More)
The way in which social conventions emerge in communities has been of interest to social scientists for decades. Here we report on the emergence of a particular social convention on Twitter—the way to indicate a tweet is being reposted and to attribute the content to its source. Initially, different variations were invented and spread through the Twitter(More)
Social networks have many counter-intuitive properties, including the " friendship paradox " that states, on average, your friends have more friends than you do. Recently, a variety of other paradoxes were demonstrated in online social networks. This paper explores the origins of these network paradoxes. Specifically, we ask whether they arise from(More)
Email is a ubiquitous communications tool in the workplace and plays an important role in social interactions. Previous studies of email were largely based on surveys and limited to relatively small populations of email users within organizations. In this paper, we report results of a large-scale study of more than 2 million users exchanging 16 billion(More)
The way in which social conventions emerge in communities has been of interest to social scientists for decades. Here we report on the emergence of a particular social convention on Twitter---the way to indicate a tweet is being reposted and attributing the content to its source. Despite being invented at different times and having different adoption rates,(More)
Consumer spending accounts for a large fraction of economic footprint of modern countries. Increasingly, consumer activity is moving to the web, where digital receipts of online purchases provide valuable data sources detailing consumer behavior. We consider such data extracted from emails and combined with with consumers' demographic information, which we(More)
If classifiers are selected from a hypothesis class to form an ensemble, bounds on average error rate over the selected classifiers include a component for selectiv-ity, which grows as the fraction of hypothesis classifiers selected for the ensemble shrinks, and a component for variety, which grows with the size of the hypothesis class or in-sample data(More)