Structure and evolution of online social networks

Abstract

In this work, we consider the evolution of structure within large online social networks. We present a series of measurements of two large real networks, one from the friend relation within the Flickr photo sharing application and the other from Yahoo!s 360 social network. These networks together comprise in excess of 5 million people and 10 million friendship links, and they are annotated with metadata capturing the time of every event in the life of the network. We show that these networks may be segmented into three regions: singletons, who do not participate in the network, isolated communities, which overwhelmingly display star structure, and a giant component anchored by a well-connected core region that persists even in the absence of stars. We give a detailed characterization of the structure and evolution of these regions. We also present a simple model of network growth that captures these aspects of component structure. The model follows our experimental results, characterizing users as either passive members of the network, inviters who encourage offline friends and acquaintances to migrate online, and linkers who fully participate in the social evolution of the network. We show that this simple model with only two numerical parameters is able to produce synthetic networks that accurately reflect the structure of both our real-world networks.