This term could mean one of two things:
- The measure, in percent, of how many people have visited, noded, and generally participated in Everything. Since there are 13387 userids, and ~6 billion people on earth, that works out to 2.2x10^-4%. Pretty damn small.
- The measure, in percent, of how much of the Everything Database has been influenced by a specific user. More specifically, how many nodes had a writeup by a specific user.
I think I prefer the latter definition.