Copper saw a large deficit of 429,000 tonnes during the first nine months of 2011 while apparent deficit was only 170,000 tonnes, reported International Copper Study Group. The metal's output in Chile, the US and Peru dropped by 3.5% in the period. Experts explain the fall citing strikes on the copper mines in Peru and Chile. LME copper price stayed weak being 20% lower as compared to this year high of USD10,000 per tonne.