The Collapse of Complex Societies - Professor Joseph Tainter

Professor Joseph Tainter is an American anthropologist and historian studied anthropology at the University of California, Santa Barbara, and Northwestern University, where he received his Ph.D. in 1975. As of 2012 he holds a professorship in the Department of Environment and Society at Utah State University.
In this interview Professor Tainter discusses the thesis of his widely acclaimed work “The Collapse of Complex Societies”, 25 years after its publication in 1988. His book is among great classics of the study of collapse. In my view a work whose quality and relevance is comparable to Limits to Growth.
Link to his book:
https://www.abebooks.com/book-search/title/collapse-of-complex-societies/author/tainter/
We have discussed the following with Prof. Tainter:
1) What is “collapse”? What is “complexity”?
2) Can you explain your theory of decreasing marginal returns over complexity?
3) What was particularly "complex" with the Western Roman Empire?
4) Why has the Western Roman Empire collapsed while the Eastern Roman Empire has not collapsed?
5) Why do you think Western society has NOT collapsed for 1500 years now? Why has it NOT collapsed over the last 200 years?
6) What major instances of decreasing marginal returns over complexity do you observe in global modern society?
7) What do you think of “Limits to Growth” by Meadows et. al?