What is Facebook's Engagement Rate?
Ever wonder how the Facebook Engagement Rate is calculated? Me too. Constant Contact had the answer, shown here. As they point out, "The outcome illustrates the portion of your audience that is engaged with your content, consequently indicating the quality and success of your posts. Facebook will use this data to determine how many fans see future content you share on the site.
For example, if one post is reaching a significant amount of people, but not producing much engagement, the News Feed Algorithm marks the post as low quality. Too many low quality posts hurt your chances of appearing in your fans News Feed in the future."