Engagement can’t continue rising indefinitely. At some point, it has to plateau and the closer you get to the plateau, the rate of growth will naturally slow.
Most communities follow an S-Curve of growth. Participation begins slowly, hits a critical mass, and starts to grow rapidly, and then plateaus as most of the likely people to participate are already participating.
There are some exceptions. Customer support communities often explode to life simply by redirecting traffic from one channel to another. And some organisations might just have a big launch and then struggle to sustain the initial base of activity.
If you’re being asked to increase engagement, the next obvious question is to what level?
There are many ways of tackling this question.
If you’re managing a support community, then the total number of answerable questions (those not requiring a member to share personal details) is a fair place to start.
If you’re managing a success based community, where members are expected to proactively share ideas and knowledge with one another, you might try to get a figure on how many people are already doing that today (and whether that rate of growth is increasing or decreasing).
If you’re managing an interest-based community, you might look at how many people are searching for related terms today and making a rough calculation based upon that.
Ultimately, you need some baseline metric that describes the type of engagement that matters to you, how much of it is happening elsewhere today, and what the top figure looks like. Once you have these metrics, you can plot your S-Curve accordingly.
(Aside, shifting behavior is a lot easier than initiating it. If you’re asking members to do something they’ve never done before, your estimates should be a lot more conservative).