"In response, the employees proposed an emergency change to the site’s news feed algorithm, which helps determine what more than two billion people see every day. It involved emphasizing the importance of what Facebook calls “news ecosystem quality” scores, or N.E.Q., a secret internal ranking it assigns to news publishers based on signals about the quality of their journalism...Typically, N.E.Q. scores play a minor role in determining what appears on users’ feeds."
Facebook has developed an internal metric for determining the quality of a news source but they choose not to use that knowledge in how they distribute information.
New York Times