Hi Arka --

Whether investment growth is sustainable or not has everything to do with the intention of the person or entity that provided it. There are no hard and fast rules, but in general If the investment is made freely and in pursuit of a rationally achievable return it makes sense to view it as sustainable..

In china's case, nearly 50% of GDP comes from investment, and there is a solid argument that a significant portion of that capital is provided in one way or another by the government. That is not bad in and of itself, but the extent of it is certainly troubling.

I'm not aware of any other countries with situations roughly analogous to China, but it's always worth looking at where capital is coming from and asking whether that flow is sustainable.

Cheers and all best --

Will