We previously announced this change, and starting Monday, we will update how we measure organic reach of Pages to be more consistent with the way we calculate reach for ads. This is a change in the way that we measure reach, not a change in News Feed distribution, and other engagement metrics will remain the same. This will provide Page owners with a more precise measurement of their audience and offer a more consistent measurement methodology across both our paid and organic reach reporting. Since this is stricter reporting, some Pages may see lower reach figures than before.
We know some marketers may rely on the previous metric for their own reporting, so over the next few months we will continue to provide the old reach metric alongside the new one in the Page Insights overview section and in the Page Insights API and export.