What is behind ROI in social media marketing

Last week, we spoke in class about the ROI of the social media tools.

But what is behind those three letters?

ROI for "Return On Investment" = (gain from investment - cost of investment) / ( cost of investment)
     
       First of all, whenever you use the social media tools to market your company it is not free. Indeed it costs time, salary of the workers, equipments (computers, desk, electricity,...) or opportunity costs (you can do another thing with that money, time,...).
     
       Secondly, your gain from investment comes by the increasing number of your sales thanks the social media marketing tools.

You can measure it by correlating your sales with:

* The Click Through Rate (CTR)
* The number of followers (also called "eyeballs")
* The number of "like" on facebook
* The number of retweets on twitter
* The number of mentions (thanks to google alerts)
* Your rank in the Search Engine (like google)