As mentioned earlier, this is a well trodden field whose results depend heavily on how you choose to define collapse or decline. I didn't see any indication of that kind of discussion. Secondly, you seem to make use of historical examples as demonstrations, but without discussing the context around them (if they were even collapses!). There's a huge risk in doing that of making superficial comparisons with no actual basis in reality. This is the trap most works on the subject fall into, because it's almost impossible for any single person to have high level expertise across multiple disparate periods and history of any particular collapse is very much unsettled, expert level territory.