Wikipedia has a good summary both of the Economic history of China [1] and the Great Divergence [2] (really comes to a head with the collapse of the Qing dynasty). Although devestated by civil war and WW2, IMO China really doesn't descend into complete craziness until the Great Leap Forward and the Cultural Revolution [3] that devastated China economically, socially, and culturally (lost generation, send-down movement, red guards, etc).
[1] https://en.wikipedia.org/wiki/Economic_history_of_China_befo...
[2] https://en.wikipedia.org/wiki/Great_Divergence#China
[3] https://en.wikipedia.org/wiki/Economic_history_of_China_(194...
ED: outside getting a book, the main characteristic to look at is China having the lion's share of historical world GDP, especially during the Yuan and Ming dynasties. The Spanish Empire gained much of its early wealth from Ming China's seemingly insatiable demand for the silver it found in South America - like thousands of pounds at a time.
Do you have any further reading on this? It doesn't strike me as too crazy of a statement - but I'd be very interested in seeing how one would go about actually quantifying it.