One metric we often track is level of activity per active member (no. posts / no. members making those posts each month)
In short, how engaged are the members who are participating?
But this metric needs context to be useful.
For example, if the level of activity per active member is rising, is this a good or a bad thing?
Well, it depends. It could mean one of three stories:
1) Story 1: Members are finding the community more engaging than before. That’s usually a good thing.
2) Story 2: Fewer members are contributing to the community and you’re left with just the more dedicated members.
3) Story 3: Some combination of the above (i.e. fewer members who are participating more).
The challenge is to identify which story is true by looking at whether the overall number of contributors has risen or fallen during the same timeframe.
If your current members are less engaged than before, find out why. Are they visiting less frequently? Do they not know the answers to questions? Are they finding the posts less interesting? What kind of topics are relevant and important to them today.
If fewer members are contributing, find out why. Are fewer newcomers reaching the community? Are they staying around for less time? What has changed in the behavior?
Activity per active member is a great metric to track (even better when you can separate it by percentage). But you have to interpret the data properly.