Long-term evolution of email networks: Statistical regularities, predictability and stability of social behaviors

TL;DR

This study reveals that despite the unpredictable microscopic changes in social ties, macro-level email networks exhibit stable statistical regularities and individuals maintain consistent social behaviors over years.

Contribution

It demonstrates long-term statistical regularities in social network evolution and the stability of individual social signatures despite tie randomness.

Findings

Social ties show exponential decay in weight variations over time.

Individuals' social signatures remain stable over several years.

Macro network patterns are statistically predictable despite microscopic unpredictability.

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.