Dr. Michael Wu, Ph.D. is Lithium's Principal Scientist of Analytics, digging into the complex dynamics of social interaction and online communities.
He's a regular blogger on the Lithosphere and previously wrote in the Analytic Science blog.
You can follow him on Twitter at mich8elwu.
If you've ever managed a community you've probably heard of the "90-9-1 rule". If you have observed a community closely, you have probably seen it in action.
Soon after a community launches, users begin to participate, but each user participates at a different rate. The minute difference in participation levels is accentuated over time, leading to a small number of hyper-contributors in the community who produce most of the community content.
The 90-9-1 rule simply states that:
But how real is this rule? Do all communities follow this rule consistently? If not, how far off is the deviation? Is the proportion really 90:9:1, or is it more like 70:25:5, or 80:19.99:0.01? Let's find out...
Lithium has accumulated over 10 years of user participation data across 200+ communities, so we can address this question empirically with rigorous statistics. Rather than complicating the issue with the lurkers, I choose to analyze only the contributors (i.e. the 9% occasional-contributors and the 1% hyper-contributors). The proportion between these two groups of participants should be 9:1 or equivalently 90:10 according to the 90-9-1 rule.
The 9-1 Part of the 90-9-1 Rule
So the 90-9-1 rule excluding the lurkers says that:
What does the data tell us? On average, the top 10% of contributors (the hyper-contributors) generate 55.95% of the community content, and the rest of the 90% (the occasional-contributors) produces the remaining 44.05% of the content.
With my statistician hat, you know I can't possibly be satisfied with just the average! So I plotted the distribution of content contributed by occasional-contributors versus the hyper-contributors across all communities. The standard deviation is 13.02%.
Please note: The reason you only see 143 communities here, is because I've excluded communities that are less than 3 month old (these communities are too young that their participation dynamics are not stable enough for the analysis).
As you can see from the data, the hyper-contributors can contribute anywhere from about 30% to nearly 90% of the community content with an average of 55.95%. This is certainly a substantial percentage (considering the fact that it is generated by only 10% of the contributors), so the 90-9-1 rule "sort of" holds. But, to be rigorous, it depends on what do you mean by "most" of the community content.
If "most" meant at least 30% of the community content, then the 9-1 part of the 90-9-1 rule holds for 99.30% of our communities. If you meant at least 40% of the community content, then 89.51% of our communities satisfy this rule. But if "most" meant at least 50% of the community content, then only 65.73% of our communities are described by this rule.
Turning the Problem Around
This gives us a convenient spot to turn the problem around and look at the 90-9-1 rule from another perspective. We can define rigorously what "most" means (e.g. at least 30% of the community content), then calculate the fraction of contributors who generated these content and treat them as the hyper-contributors. We can then compare and see how far off we are from the expected ratio of 9:1.
Averaging across 143 communities, we see that if we define "most of the community content" to be "at least 30% of the total content," then the fraction of participants who contributed this amount ranges from 0.32% to 5.14% with an average of 2.73%. That means, on average, hyper-contributors consist of roughly 2.73% of the contributing population, so the remaining 97.27% of the participants are occasional contributors. And the ratio of hyper- to occasional-contributors is about 97:3, far from the expected value of 9:1.
If instead, we define "most" to be "at least 40%" of total content, then we get roughly 5.07% hyper-contributors on average across 143 communities. Now the ratio of hyper- to occasional-contributors is about 19:1, which is closer but still quite far off the expected ratio of 9:1.
If we defined "most" to be "at least 50%" of the total content, then the group that contributed this amount (which qualifies them to be hyper-contributors) is about 9.35% of the participants. This gives us a ratio that is much closer to the expected value of 9:1 on average. However, the variability is also very large. Even under this simple criterion of contributing at least 50%, the fraction of participants who contributed this amount may vary from less than 1% to ~18% of the participants. That means the ratio between hyper- and occasional-contributors may be anywhere from 99:1 to about 5:1.
So is 90-9-1 a hard and fast rule? Definitely not! Not even the 9-1 part of it. But it is certainly a great rule of thumb, when looking at or explaining community data. And it tells us that participation in communities is highly skewed and unequal, and there is a small fraction of hyper-contributors who produce a substantial amount of the community contents.
Next time I am going to start to dive deeper into the contribution level of the hyper-contributors, your community's real superusers.
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