Via Mari Smith FB Page
Facebook Page owners can now see POST-level metrics that apply *solely* to people who like your page, a.k.a. just your FANS!
Previously, your Insights included fans + non fans (ever since Facebook made it so anyone can post on fan pages without first liking the page).
The separation of this data between fans & non-fans allows you to accurately measure your engagement rate, virality, and reach, specifically regarding the people that actually matter to you: your fans!
To access this data, you'll need to export your Insights. Read more on PostRocket's great post here: http://blog.getpostrocket.com/2012/08/this-just-in-majo