Facebook engagement rates fall as your fan base gets higher. At first sight that seems odd. But of course it isn’t.
Most people tend to engage with brands infrequently on social media. Seduced by a particular post they may “Like” it on a whim, but then stay away from your page. They have little motivation to comment on or share other posts unless they are real fans. And of course unless you are spending serious money, chances are they won’t see those other posts.
So most Facebook “engagements” come from people who have recently become fans. The larger your fan base, the longer your “average” fan has been with you; and because of that, larger fan bases have lower engagement rates.
This is a problem for people using a common metric for evaluating social media effectiveness: the formula “Likes + Share + Comments / Fans” as it can make it look as though your campaigns are getting worse over time.
So how can you evaluate effectiveness on Facebook and other social media platforms? There are a couple of ways.
First there are some comparative measures. For instance you might want to compare engagement rate of different types of posts or different campaign themes. This won’t solve the problem of lower engagement rates with larger fan bases but it will help you focus on improving your campaigns.
Second you can measure engagement of recent fans. By dividing the number of engagement actions (shares, likes, comments) in any one period by the number of new fans acquired in the same period you will get a useful measure of true engagement that should be comparable across time periods.
Purists might argue that the engagement actions in any one period may be coming from people who became fans in an earlier period. That’s true; but I am not sure it matters much. For a start it is probable (at least, if you are using a period of 1 month rather than 1 day) that the number of actions from “old” fans will be low; but also if you compare different months you will be comparing like with like.
Ultimately though, “engagement” on social media is a measure of limited value. So what if people have engaged with you? What matters is their behaviour. Measuring that by using your web analytics to track visits generated from social media together with dwell time, page depth, loyalty and conversions is a far better way of measuring the effectiveness of your social media campaigns.