Analysis of a Reciprocal Network Using Google+: Structural Properties and Evolution

Many online social networks such as Twitter, Google+, Flickr and Youtube are directed in nature, and have been shown to exhibit a nontrivial amount of reciprocity. Reciprocity is defined as the ratio of the number of reciprocal edges to the total number of edges in the network, and has been well studied in the literature. However, little attention is given to understand the connectivity or network form by the reciprocal edges themselves (reciprocal network), its structural properties, and how it evolves over time. In this paper, we bridge this gap by presenting a comprehensive measurement-based characterization of the connectivity among reciprocal edges in Google+ and their evolution over time, with the goal to gain insight into the structural properties of the reciprocal network. Our analysis shows that the reciprocal network of Google+ reveals some important user behavior patterns, which reflect how the social network was being adopted over time.