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Activity is a lesser requirement next to Merits, since the Merit System kicked-in, and most people are stuck either waiting for their first merit, or having enough merits to reach their next rank.
As an example, this is the current status of users that are currently Full members, have earned at least 1 merit, and are in the pipeline to reach Sr. Member (your minimal declared target):
segment nUsers
1. Could have ranked up to Sr. Member, lacking Merit 2976
2. Could have ranked up to Sr. Member, lacking Activity 30
3. Soon may rank up to Sr. Member 2
4. Not enough activity nor Merit to rank up to Sr. Member 898
The vast majority have reached the required Activity, but lack sufficient Merits, so the latter is generally most difficult to achieve. There are bags more that have not earned a single Merit yet.