The Structure of Online Social Networks Mirror Those in the Offline World

TL;DR

This study demonstrates that online social networks on Facebook and Twitter exhibit layered structures similar to offline face-to-face networks, with comparable sizes and contact frequencies, confirming the mirroring of offline social patterns online.

Contribution

It provides the first large-scale empirical evidence that online ego-centric networks mirror offline layered social structures, including an additional innermost layer.

Findings

Online networks have four to five-layer structures.

Layer sizes and contact frequencies closely match offline data.

An innermost layer of about 1.5 alters exists in online networks.

Abstract

We use data on frequencies of bi-directional posts to define edges (or relationships) in two Facebook datasets and a Twitter dataset and use these to create ego-centric social networks. We explore the internal structure of these networks to determine whether they have the same kind of layered structure as has been found in offline face-to-face networks (which have a distinctively scaled structure with successively inclusive layers at 5, 15, 50 and 150 alters). The two Facebook datasets are best described by a four-layer structure and the Twitter dataset by a five-layer structure. The absolute sizes of these layers and the mean frequencies of contact with alters within each layer match very closely the observed values from offline networks. In addition, all three datasets reveal the existence of an innermost network layer at ~1.5 alters. Our analyses thus confirm the existence of the layered structure of ego-centric social networks with a very much larger sample (in total, >185,000 egos) than those previously used to describe them, as well as identifying the existence of an additional network layer whose existence was only hypothesised in offline social networks. In addition, our analyses indicate that online communities have very similar structural characteristics to offline face-to-face networks.