An organisation's Twitter account is very different to a personal one. Whilst the latter may primarily function as a means of keeping up to date, for organisations like libraries, the point of using a tool like Twitter should be to generate real interaction and engagement with your users. Consequently, this is what you should be trying to capture when evaluating impact, not whether you have 50 or 5,000 followers.
Real life examples, exchanges and vignettes that show evidence of real engagement can offer much greater insight than a simple statistic. As well as this richer qualitative data, some quantitative measures such as how many people are tweeting @you or retweeting you are also useful. This shows that people value the content that you are sharing, and thus are more likely to continue to follow and interact with you, building closer and longer-lasting relationships. You can also measure how many users are being referred to your library website, blog or databases via Twitter, to assess if the tool helps to directly drive traffic to your resources and services. Map the network of your followers and see how it fits with your library's strategic positioning.
That said, it is still very difficult to show the value of Twitter in a way that is often required in an annual report - a quick bottom line or a headline statistic. However, at the very least, I would strongly recommend trying to avoid the trap of using the following metrics to demonstrate value and impact.
The Wrong Metrics
1. Total Number of Followers:
This is one of the easiest measures to obtain, but also perhaps the most flawed. Firstly, it is an easy statistic to manipulate: simply follow more people. Although following 100 people will probably only result in 20% or so reciprocal follow-backs at most, it is still a quick way to increase your absolute number of followers. Clearly however, an increase of this nature is meaningless. Moreover, the quantity of followers gives no indication of the quality of your followers. For instance, are they actually library users or other stakeholders, i.e. people you are interesting in connecting with? Therefore, what might look like a pretty upward sloping line on a graph really tells you very little about the value of your library's Twitter account.
2. Followers to Following ratio:
But surely you need to compare your number of followers with the number of people you follow in order to provide a relative and meaningful measure? And a higher ratio means your account must be great, right? Well, yes and no. Looking at this ratio is certainly a valuable metric, but if you a believe a higher ratio is always a good thing, you may be missing the point of Twitter.
Twitter is about engaging with your users, that means following them back when they take the time to follow you. This demonstrates that you are actually interested in your users' information and what they have to say. If you aren't following the majority of your followers, what kind of a message does this send out? It is different for personal accounts (particularly celebrities, where an extremely high ratio of followers is expected for obvious reasons), but when you are specifically trying to build relationships with your users as an organisation or a business, showing interest in them is key. This doesn't mean that your ratio has to be exactly one, but is should be close to it: this sends out a signal that you are not just racking up as many followers as possible who you can broadcast information to, but instead are actually interested in engaging, communicating and sharing with your users as a two-way process.
3. Number of Tweets
In the same way that looking at your total number of followers is of limited value, measuring the number of times you tweet is similarly flawed. Tweeting should be about sharing content and information that contributes something to your network. If you are not adding value through your tweets there is little point, in fact, excessive tweeting may even turn people off by filling up their Twitter stream with irrelevant content. Therefore looking at retweets of, and replies to, your content is a much better measure, as it shows the kind of content that actually engages your users. You can also use this valuable feedback to direct and shape how you use Twitter for your library. What works? What doesn't? Pay attention to your followers in an honest and authentic way and they will tell you.