Total trade ... was ~179 kBTC. ...China's slice ... is 90%.
Given the isolated nature of the on-shore RMB market, I would be inclined to simply drop it from volume numbers. If you could measure the fiat in-/out- flows, it would be informative, at least as a measure of sentiment in China, but what actual informative value does a costless swap between traders in a captive arena convey? Call me unimaginative in this case, if you will, but I see none.
Yes, bitcoin volumes are very low relative to the recent manic and crash periods. This is clearly good information. It means that liquidity is poor on the exchanges. This should not be surprising. After the collapse of what was once the flagship exchange, hoi polloi are cautious and hesitant about using exchanges. Much volume has moved off-exchange. New adopters with whom I have spoken recently purchased their coins via local transactions. Certainly BIT has systematically sought to secure off-exchange supplies. Hedge funds are purchasing subscriptions with miners now -- I have personal knowledge of such cases -- in part, in order to avoid exchanges.
To capture actual volumes of exchange one must go off-exchange, at this point. Those numbers are more difficult to collect, but they remain transparent in the blockchain, if you can identify the corresponding transactions.