At the beginning of this month, Facebook announced that they were rolling out advanced analytics that would make it possible to measure performance at a level higher than simply on specific posts.
This will allow page admins to see things like the actions people take on the pages themselves, including the number of follows and unfollows, likes and unlikes, and more. They are also adding an impression view to posts, so you can see exactly how many people saw the post.
The ability to see specific actions on a page will allow you to create targeting segments based on those actions, so, for example, you could have an audience of people who unliked the page, and target them in an attempt to re-ignite their interest.
These new segments will help you track conversions from engagement with your page to purchase actions, compare demographics for audiences based on channel or a specific activity, and similar refinements of the available data.
In addition to the Facebook analytics updates, Facebook is also rolling out a similar analytics functionality to Instagram to help advertisers create segments there too, as well as the retention rates of people who comment on or like posts, etc.
At the moment, the new analytics tools for Facebook and Instagram are still in the beta testing phase, but page admins can request an invitation to the new tools.