Copper is sinking to its lowest price since October 2011, as the outlook for the global economy continues to weaken.

Copper fell 11.8 cents to $3.1875 a pound, a drop of 3.6 percent.

Prices for other industrial metals and energy futures also fell.

Crude oil extended a weeklong slide, losing $2.04 to $86.68 a barrel. That's down almost $8 a barrel from a week ago.

The latest blow to investors' confidence came when the International Monetary Fund lowered its outlook for the world economy this year. The IMF said government spending cuts will slow U.S. growth and keep Europe in a recession.

Also this week China reported economic growth that was slower than investors expected. China is a huge importer of basic materials like copper.

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