Copper

Glencore, Anglo American and BHP Billiton hoped that diversifying would work.

From coffee to copper to corn, the price of commodities has fallen over the past year.

Exports from big states like Texas, California and Michigan have soared since the 1990s when the North American Free Trade Agreement opened U.S. markets to Mexico. But not every state has been as savvy promoting cross-border trade.

Shares of BHP Billiton are down this morning, after the mining giant saw profits fall for the first time in three years.