Production increased, demand decreased. This is an oversimplification of the copper market but I think it's worth considering.
Source: http://www.icsg.org/index.php/64-icsg-releases-new-edition-of-the-directory-of-copper-mines-and-plants (Report from 20th Jan 2016).
In developing its global market balance, the ICSG uses an apparent demand calculation for China—the leading
global consumer of copper accounting for about 45% of world demand (...). In the first ten months of 2015, world apparent usage is estimated to have declined by around 1% (210,000 t) compared with that in the same period of 2014. Excluding China, world usage declined by around 3.5%. Although Chinese apparent demand increased by around 1.5%, usage declined by 4.5% and 7% in the EU and Japan, respectively, and by 46% in Russia (following the withdrawal of Russia’s cathode export tax in September 2014). On a regional basis, usage is estimated to have increased by around 1% in Africa, in Asia and in the Americas, respectively while declining by around 10% and 60% in Europe and Oceania, respectively. World refined production is estimated to have increased by about 1.8% (330,000 t) in the first ten months of 2015 compared with refined production in the same period of 2014: primary production was up by 2% and secondary production (from scrap) remained essentially unchanged. .