title: Long-Term Evolution of Email Networks: Statistical Regularities, Predictability and Stability of Social Behaviors.
abstract: In social networks, individuals constantly drop ties and replace them by new ones in a highly unpredictable fashion. This highly dynamical nature of social ties has important implications for processes such as the spread of information or of epidemics. Several studies have demonstrated the influence of a number of factors on the intricate microscopic process of tie replacement, but the macroscopic long-term effects of such changes remain largely unexplored. Here we investigate whether, despite the inherent randomness at the microscopic level, there are macroscopic statistical regularities in the long-term evolution of social networks. In particular, we analyze the email network of a large organization with over 1,000 individuals throughout four consecutive years. We find that, although the evolution of individual ties is highly unpredictable, the macro-evolution of social communication networks follows well-defined statistical patterns, characterized by exponentially decaying log-variations of the weight of social ties and of individuals' social strength. At the same time, we find that individuals have social signatures and communication strategies that are remarkably stable over the scale of several years.
authors.affiliation: Departament d'Enginyeria Química, Universitat Rovira i Virgili, 43006 Tarragona, Catalonia, Spain.
authors.forename: Antonia
authors.initials: A
authors.lastname: Godoy-Lorite
authors.affiliation: Departament d'Enginyeria Química, Universitat Rovira i Virgili, 43006 Tarragona, Catalonia, Spain.|Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona, Catalonia, Spain.
authors.forename: Roger
authors.initials: R
authors.lastname: Guimerà
authors.affiliation: Departament d'Enginyeria Química, Universitat Rovira i Virgili, 43006 Tarragona, Catalonia, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Sales-Pardo
mesh_terms: D001499:Bayes Theorem; D034742:Electronic Mail; D006801:Humans; D012919:Social Behavior; D060756:Social Networking