Planeplotter aircraft reports are now deduplicated before being counted in stats. This is needed to correctly handle some cases of bad data being fed via planeplotter.
It will reduce the number of reports counted from planeplotter receivers by approx. 20-30% from 6 Jan onwards, so if you are feeding via planeplotter and you see a drop in reports, it’s normal and it doesn’t indicate a problem with your feed.
The reports that are no longer counted are duplicates of previously-reported data which planeplotter continues to report for several minutes after the data stops being updated (e.g. after aircraft leaves the receiver range). These reports are ignored by FlightAware’s normal processing anyway (it is duplicated, stale data) and the same now applies to stats.
The aircraft report counts aren’t used for the ranking in the stats table and aren’t generally comparable between different receiver types (before or after the change).