Facebook: organic reach calculations will depend on viewability
Facebook has introduced changes in the measurement of organic reach of brand pages. Until now it relied on a counting of the number of times that a post appeared in the newsfeed. As of now (Feb 2018), the reach value will depend on the number of times that the post appears on screen. According to Facebook may the new process have an impact on stats van some brand pages, resulting in lower values than in the past.