SHANGHAI, Dec 9 (SMM) - Copper inventories in the domestic bonded zone added 4,200 mt from December 2 to 32,600 mt on December 9, according to SMM survey. Inventory in the Shanghai bonded zone grew 4,200 mt to 29,200 mt, while that in the Guangdong bonded zone remained unchanged. The increase in inventory this week was contributed by the exports of domestic smelters and the arrivals of the bill of lading at bonded zone warehouses. Smelters were more willing to export their goods amid the opening of the export window. However, inquiries of goods under the bill of lading at ports were extremely sluggish owing to the low SHFE/LME copper price ratio. Traders had to move their goods into the bonded zone warehouses amid the dropping Yangshan copper premiums.