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I searched the web for info on Google site count fluctuations and corpus rotations, but didn't find much.
What do you guys think? Is Google rotating corpuses?
It also might mean that Google untangled a duplicate url canonical url issue for your domain, or that pages were actually dropped, or that... well, it can be a mystery, too, because accuracy in that report is not a top priority at the 'plex. The general user is rarely concerned with it, and the general user is their priority #1.
Even for sites with no major problems I see site counts cycling from 80% to 98% of the true number of URLs - even for sites that have never had any sort of canonical problem, and never had a 404 error.
Traffic remains stable and has actually gone up which is the exact opposite of what should happen when you drop 60,000 pages out of the index so imho the site: command is just more fuzz just like the tbpr and link: command.