1) Small groups have higher numbers of core users

2) Private and semi-public groups have higher numbers of core users than public groups

3) People in private groups remain in the core for longer

4) A user who is in the core of one group is more likely to become a member of the core when joining another group

5) New members who eventually become part of the core are more likely to receive messages from other users who have been long-time core users

6) New members who eventually become light users are more likely to receive messages from other light users, if they receive replies at all.

This suggests some strategies for building a strong group of core users to transmit social norms. For example, having an idea of who the core users are in other similar communities and making a special effort to reach out to them if they visit your site.

Unhappily I lost the original paper and all I have are my notes, so I don't know exactly how they defined the core users offhand.