Community membership consistency applied to corporate board interlock networks

TL;DR

This paper introduces a metric for assessing the reliability of individual node community memberships in social networks, demonstrated on corporate board interlock networks to reveal core and fringe countries within global business communities.

Contribution

It proposes a novel community membership consistency metric that accounts for non-deterministic community detection results, providing more reliable node-level community insights.

Findings

Core countries form persistent communities linked by geography and culture

Fringe countries associate with multiple global business communities

Community structure reflects geographical and cultural proximity

Abstract

Community detection is a well established method for studying the meso scale structure of social networks. Applying a community detection algorithm results in a division of a network into communities that is often used to inspect and reason about community membership of specific nodes. This micro level interpretation step of community structure is a crucial step in typical social science research. However, the methodological caveat in this step is that virtually all modern community detection methods are non-deterministic and based on randomization and approximated results. This needs to be explicitly taken into consideration when reasoning about community membership of individual nodes. To do so, we propose a metric of community membership consistency, that provides node-level insights in how reliable the placement of that node into a community really is. In addition, it enables us to distinguish the community core members of a community. The usefulness of the proposed metrics is demonstrated on corporate board interlock networks, in which weighted links represent shared senior level directors between firms. Results suggest that the community structure of global business groups is centered around persistent communities consisting of core countries tied by geographical and cultural proximity. In addition, we identify fringe countries that appear to associate with a number of different global business communities.