First the 11% (7 participants) who are not subscribed to any mailing list:
Preference between mailing list and forum for people not subscribed to any mailing list
Potential for increase of interaction with the RIOT community for people not subscribed to any mailing list
Preferred chat-based communication for people not subscribed to any mailing list
For the 22% who never participated in a discussion on the mailing list:
Preference between mailing list and forum for people who never participated in a discussion on the mailing list
Potential for increase of interaction with the RIOT community for people who never participated in a discussion on the mailing list
Preferred chat-based communication for people who never participated in a discussion on the mailing list
For the potential of of interaction with the RIOT community I also found the inverse sub-set interesting