The reason that the reach fluctuates is because it is calculated as a rolling average. What you see on the leaderboard under the ‘Reach’ column is the average reach per post shared by that specific user, and it is calculated over a 30-day period. This includes both the number of followers that a user has, as well as the number of followers of any other person who may reshare his/her posts.

Even if you are sharing more posts to your social channels compared to the previous 30 days, your average reach could decrease because no one is resharing your posts, or the people who have reposted them have a lower number of followers compared to people that had previously reshared them, which would then bring the average down. Your average reach will also depend on which social networks you share to; for example LinkedIn caps the number of people reached at 500, bringing your average down if you have a lot more followers.

Please note that reach is intended as a potential estimate to give you an indication of the popularity of your content.
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