How are the "Most Active Members" determined?

The "Most Active Members" information is considered over the life of the Groupsite (since its inception). We count as "activity" all the things that generate a line item on a Recent Activity Update (i.e., a member replies to a discussion post, RSVPs for an event, sends an email blast, changes their profile picture, adds an objective, etc.) to determine and generate the members you see in the "Most Active Contributors" view of the "Members" type content module.