I'm skeptical about comparing zero fee volume to non-zero fee volume.
To be clear: for short to mid term trading purposes, I absolutely don't doubt the relevance of CNY volume.
But for the longer term view of market volume, in my opinion, the "costly" volume of the three big USD exchanges is a good measure of how much money is "flowing into the market". (Sidenote: I really need to include Coinbase from now on)
That said, I know just discarding CNY (or permanently zero-fee USD) volume is not ideal. I have been trying to come up with ways to 'discount' the Chinese volume by some factor to make it comparable, but nothing ever really came out of it that looked satisfying to me.
Is there a relation between exchange volume and the amount of money coming into the system (or being drained from it)? Volume is generally up when the price is changing, up or down; and that may be cause and effect at the same time. But figuring ot the net input money flow seems to be a complicated computation at least...
I would think that, in China, money is steadily leaving the system: Chinese traders seem to be gradually selling and taking their cash out of the exchanges. This feeling is not based on the exchange volumes, but simply becuse of the decay of the China bubble (which seems to be too fast to be due to miner dumping alone). The rest of the world should still be a net buyer, but there is no data, really, and apparently it can barely absorb what the Chinese and the miners are selling.
There is no "money" entering nor leaving the bitcoin system. Bitcoin is money, so is USD, CNY etc. What happens is that
moves from one money system to another. When the revaluation of money system is not the same in all actors' minds, there has to be trades. If all actors at the same time and to the same degree change their valuations, there need not be many trades.