And even then 275 of 1678 FC Houses on Zodiark having less or exact 3 Members. This accounts for a total of 16,38% of all FC Houses or of 4,77% of all total available plots before Patch 6.1. If we assume that all of those 275 are just abondened shell FCs and not one Single Player FC which uses their FC-House on a regular basis i'm still not sure where your 80% came from.