This is a topic that has been getting a lot of discussion at the Online Community Summit in Sonoma today. Hearing a bunch of ideas, but want to get your opinion as well.
From the online commnity summit crowd:
* a combination of growth over time of traffic, content, and users
* number of new advocate/influencers
* increased loyalty
* amount of traffic
Each community SHOULD have their own algorithm for calculating CHI (Community Health Index) what is yours and what do you call it besides community health index. I've heard engagement metrics, etc.
I know this is an old discussion - although I'm not sure that a post with no replies counts as a discussion... ;-)
One metric that I would want to track would be: # of discussions with more than "n" participants
...where "n" is some number that I (as a community manager) can plug in and increase as I tracked community growth over time.