Long-term changes in prices, wages and the size of the monetary economy in pre-industrial China 1000-1770

Would historians have viewed China in the post-Song time as a transition from a major leading civilization towards a stagnant agrarian empire, even though it still could sustain a population as large as 0.3 billion in 1775. In a seminal comparative study of economic growth in world history, the economic historian Eric Jones makes the startling argument that Song China exhibited intensive growth (economic growth per capita), preceding both Tokugawa Japan and seventeenth-century Britain by more than five centuries. While Jones does point to the rise in real income per capita during the Song period, it seems to me that one of the implicit questions generated by his study is the following: why did the intensive growth fail to continue in the ensuing dynasties? Were social upheavals such as the Mongol invasion one crucial factor in this downward turn?