Note: I have not published blog posts about my academic papers over the past few years. To ensure that my blog contains a more comprehensive record of my published papers and to surface these for folks who missed them, I will be periodically (re)publishing blog posts about some “older” published projects.

It seems natural to think of online communities competing for the time and attention of their participants. Over the last few years, I’ve worked with a team of collaborators—led by Nathan TeBlunthuis—to use mathematical and statistical techniques from ecology to understand these dynamics. What we’ve found surprised us: competition between online communities is rare and typically short-lived.

When we started this research, we figured competition would be most likely among communities discussing similar topics. As a first step, we identified clusters of such communities on Reddit. One surprising thing we noticed in our Reddit data was that many of these communities that used similar language also had very high levels of overlap among their users. This was puzzling: why were the same groups of people talking to each other about the same things in different places? And why don’t they appear to be in competition with each other for their users’ time and activity?

We didn’t know how to answer this question using quantitative methods. As a result, we recruited and interviewed 20 active participants in clusters of highly related subreddits with overlapping user bases (for example, one cluster was focused on vintage audio).

We found that the answer to the puzzle lay in the fact that the people we talked to were looking for three distinct things from the communities they worked in:

1. The ability to connect to specific information and narrowly scoped discussions.
2. The ability to socialize with people who are similar to themselves.
3. Attention from the largest possible audience.

Critically, we also found that these three things represented a “trilemma,” and that no single community can meet all three needs. You might find two of the three in a single community, but you could never have all three.

Figure from “No Community Can Do Everything: Why People Participate in Similar Online Communities” depicts three key benefits that people seek from online communities and how individual communities tend not to optimally provide all three. For example, large communities tend not to afford a tight-knit homophilous community.

The end result is something I recognize in how I engage with online communities on platforms like Reddit. People tend to engage with a portfolio of communities that vary in size, specialization, topical focus, and rules. Compared with any single community, such overlapping systems can provide a wider range of benefits. No community can do everything.

This work was published as a paper at CSCW: TeBlunthuis, Nathan, Charles Kiene, Isabella Brown, Laura (Alia) Levi, Nicole McGinnis, and Benjamin Mako Hill. 2022. “No Community Can Do Everything: Why People Participate in Similar Online Communities.” Proceedings of the ACM on Human-Computer Interaction 6 (CSCW1): 61:1-61:25. https://doi.org/10.1145/3512908.

This work was supported by the National Science Foundation (awards IIS-1908850, IIS-1910202, and GRFP-2016220885). A full list of acknowledgements is in the paper.