"Engagement ratios can drive a lot of your social analytics insight. How many people click a link? What proportion of people stay on your blog over a certain time? What is the engagement compared to reach of your updates?"
— When you get past the basic descriptors - like followers, subscribers, and downloads - ratios can be a strong indication about how your audience is engaging with your content and your social media projects. Positive growth in ratios will bring positive growth in social media roi.