To lie about the stats for specific countries would involve the cooperation of numerous high-ranking JWs
True. Each country compiles its numbers on Sep 28th and sends it to the HQ by Sep end for the entire service year. Locally, Three service desk secretaries compile the number which then gets reviewed by the the Desk overseer and the subsequent branch committee member who is responsible for the Service Department.
So if the number is fudged by half a million, it would take a dozen or so branches to fudge these and many individuals from one branch will know of it when the fudged numbers get published in the yearbook. This is true for the partakers too- if they are increasing, they have to report it truthfully.