I don't know what you mean by "About a year ago, the levels were as low as they are now and it didn't seem to do a thing." A year ago, the LME stocks were around 600,000 tons - today they are at 216,000 tons.

The intestesting thing is that SHFE and CME warehouse stocks are also very close to 5 year lows.

However, I agree that I too haven't seen the "shortage in warehouse levels would eventually drive a price increase in copper". There is a big disconnect to me that I don't understand.

There are apparently "hidden" warehouses in China....

We believe that large volumes of collateralised financed metal are being held in bonded warehouses not only in Shanghai, the focus of most bonded estimates, but also in other Eastern Seaboard port cities. We also believe that metal might be being held in ‘hidden stocks’, essentially in the form of on-shore customs cleared stocks, which we believe are being used by some Chinese corporates as a collateral tool to secure loans at reduced interest rates.

from: http://ftalphaville.ft.com/2014/02/21/1778262/still-waiting-for-that-china-copper-unwind/

But I still don't get it - the three known warehouses are at 5 year lows... But becuase of something unknown - the market drives the price down.