Upworthy have released the code they use to track user engagement, with a nice bit of methodology explaining what they’re tracking and why they care:
“In the age of ever-present social media, our collective attentions have never been spread thinner. According to Facebook, each user has the potential to be served 1,500 stories in their newsfeed each time. For a heavy user, that number could be as much as 15,000. In this climate, how do you get people to pay attention? And, more importantly, how do you know they’re actually engaged?
“Clicks and pageviews, long the industry standards, are drastically ill-equipped for the job. Even the share isn’t a surefire measure that the user has spent any time engaging with the content itself. It’s in everyone’s interest — from publishers to readers to advertisers — to move to a metric that more fully measures attention spent consuming content. In other words, the best way to answer the question is to measure what happens between the click and the share. Enter Attention Minutes.”