Year(s) of such "well-documented" collapse(s) ? Please mention which ones you have in mind, thank you. [Pay attention children, Uncle Twatter has some stories for our tea party]
Nice: "Frequently...decentralization of authority after a 'classic' period of centralized social order, perhaps replaced by competing centers as the central authority weakens."
Some might argue that USSR was merely a State collapse as opposed to a societal collapse. Belarus looked just fine when I visited. The Russians won't let me visit, yet, so...