The 90-9-1 theory explains the percentage of a wiki's participation, breaking it down as readers being the highest percent, with minor contributors composing the 9 percent and enthusiastic and active contributors composing 1 percent of the total participants in a wiki.

In his article titled Participation Inequality: Encouraging More Users to Contribute, Jakob Nielsen explores a phenomenon which affects most online, multi-user communities that rely on users to contribute. Participation Inequality is the tendency for most users to participate very little (if at all) and a few members of the community to account for a disproportionately large amount of the content and activity.

When studied, it was found that user participation generally follows a 90-9-1 Rule:

• 90% of users are “lurkers” (i.e. they read or browse but don't contribute)
• 9% of users contribute from time to time , but other priorities dominate their time
• 1% of users participate very often and account for most of the contributions

This concept is very applicable to a wiki environment because contribution is fundamental to a wiki's success. While it is impossible to overcome this type of human behaviour, it is possible to change the participation distribution (i.e 80-16-4 where 80% are lurkers, 16% contribute a little and 4% contribute the most). Some ways to equalize participation in a wiki include:

• Making it easier to contribute. Offering a wiki help centre, tutorial information and resources for users can help familiarize users with the environment and allow them to feel more comfortable contributing
• Encouraging editing over creating. For most new users, the thought of a blank white page is frightening. Instead, offer templates and examples which users can reformat to fit their content without having to come up with everything themselves.
• Reward participants. Identify your contributors and reward them using small incentives (i.e. gold stars on personal spaces, or Duke Stars on sun forums).

Some wiki examples show variances in these percentages, but as described above, certain best practices can shift the participant percentages. Here are two examples with percentages.

Wikipedia. The Wikipedia article Who Writes Wikipedia by Aaron Swartz discusses the claims made by Jimbo Wales that on Wikipedia, “over 50% of all the edits are done by just .7% of the users … 524 people.” However, Aaron Swartz describes the story he saw from his studies as this:

“When you put it all together, the story become clear: an outsider makes one edit to add a chunk of information, then insiders make several edits tweaking and reformatting it. In addition, insiders rack up thousands of edits doing things like changing the name of a category across the entire site – the kind of thing only insiders deeply care about. As a result, insiders account for the vast majority of the edits. But it's the outsiders who provide nearly all of the content.”

MSDN Community Content . While not precisely a wiki, the Microsoft Developer Network has Community Content features that are wiki-like. According to the sidebar on http://msdn2.microsoft.com/en-us/library/default.aspx as of December 20, 2007, 1866 edits out of 10851 total edits were made by the top five contributors (three of whom are Microsoft employees). That percentage is slightly above one percent at 1.72%.