What's in a Niche? Migration Patterns in Online Communities

TL;DR

This paper uncovers regular migration patterns within online communities under broad topics, revealing a directional flow that correlates with community size, toxicity, and linguistic features, across Reddit and Wikipedia.

Contribution

It introduces the concept of a partial order in user migration patterns within online topics and demonstrates how multiple movement directions collectively organize community structures.

Findings

Communities follow a consistent migration direction related to size and toxicity.

Different movement types (users, URLs, mentions) produce distinct but related directions.

Patterns are observed across Reddit and Wikipedia, supported by simulations.

Abstract

Broad topics in online platforms represent a type of meso-scale between individual user-defined communities and the whole platform; they typically consist of related communities that address different facets of a shared topic. Users often engage with the topic by moving among the communities within a single category. We find that there are strong regularities in the aggregate pattern of user migration, in that the communities comprising a topic can be ordered in a partial order such that there is more migration in the direction defined by the partial order than against it. Ordered along this overall direction, we find that communities in aggregate become smaller, less toxic, and more linguistically distinctive, suggesting a picture consistent with specialization. We study directions defined not just in the movement of users but also by the movement of URLs and by the direction of mentions from one community to another; each of these produces a consistent direction, but the directions all differ from each other. We show how, collectively, these distinct trends help organize the structure of large online topics and compare our findings across both Reddit and Wikipedia and in simulations.