The 90/9/1 rule, also known as the 1% rule or the participation inequality principle, is a concept that describes the unequal distribution of participation in online communities. It states that in any given online community, 90% of the members are passive observers, 9% are occasional contributors, and only 1% are highly active and engaged participants. This rule highlights the fact that a small minority of individuals are responsible for the majority of content creation and interaction within online communities. It serves as a reminder to community managers and moderators to foster a welcoming and inclusive environment that encourages active participation from all members.