The Chinesehave over-built Cu smelter capacity (like they do with everything). Unlike zinc, they only produce a fraction of the copper concentrate processed internally and thus are dependant upon imports to feed their smelters. There is an ongoing concentrate deficit that has driven treatment charges to record lows, to the point where some smelters have been shuttered. Miners are in the driver's seat now, and will remain there for the foreseable future.