China's imports of copper ended the 2012 boom year on a muted note, with the headline figure falling 6.6% on the month to 341,211 tonnes which was the second lowest monthly level of last year. The drop has been widely attributed to reduced end of year credit appetite from financiers, who use copper as collateral in the shadow banking sector.

Most commentators have instead focused on last month's record imports of iron ore as a sign of manufacturing recovery in the world's largest buyer of industrial raw materials.

Last year's 4.65 million tonnes of cumulative imports of copper still marked a 14% acceleration from 2011 and a new all time record, eclipsing even the 4.29 million tonnes imported in 2009, a year when imports soared on the back of post meltdown, bargain basement prices.

These preliminary figures aggregate imports of copper in various forms but it is almost certain that imports of refined metal also notched up a new record of around 3.40 million tonnes in 2012, unless there was a drastic change in November 's product ratio split.

This Chinese import boom has, however, left an unwelcome, destabilising legacy, one that will determine not only the level of imports this year but, quite possibly, the structure of the entire global copper market.

The copper market is now collectively wise to the fact that what China's customs department classifies as an import may only travel as far as Shanghai's bonded warehouse zone.

What was once little more than a statistical quirk has assumed ever greater importance as accelerated "imports" over the course of 2012 coincided with a marked slowdown in the Chinese growth story. The result has been a massive build in Shanghai bonded stocks, something in the order of 500,000 tonnes over the last 12 months.

At an estimated 800,000-900,000 tonnes they dwarf the 543,000 tonnes held at the end of December in the warehouse systems of the world's three foremost copper trading exchanges, namely the London Metal Exchange (320,500 tonnes), the COMEX (64,150 tonnes) and the Shanghai Futures Exchange (158,200 tonnes of duty-paid metal).