Federal Reserve Chairman Ben Bernanke has issued cautions about the economy. Jim Watson/AFP/Getty Images hide caption

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International Monetary Fund Managing Director Christine Lagarde announced Friday that the IMF had raised $430 billion, surpassing its stated goal. Charles Dharapak/AP hide caption

itoggle caption Charles Dharapak/AP

International Monetary Fund Managing Director Christine Lagarde made the case for an international crisis fund at a briefing in Washington on Thursday. Alex Wong/Getty Images hide caption

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Oil field workers drill into the Gypsum Hills near Medicine Lodge, Kan. Hydraulic fracturing, or "fracking," to coax out oil and gas has led to a natural gas boom that the U.S. market is having trouble absorbing. Orlin Wagner/AP hide caption

itoggle caption Orlin Wagner/AP

Job seekers attend a career fair in New York City. Federal Reserve Chairman Ben Bernanke says the quick drop in unemployment might have been a reversal of overzealous cutbacks during the financial crisis. Spencer Platt/Getty Images hide caption

itoggle caption Spencer Platt/Getty Images

A FedEx hybrid delivery truck. In FedEx's fleet of over 90,000 vehicles, 408 are hybrid or electric, and 4,000 are fuel-efficient, lower-emitting "Sprinter" vans. Courtesy of FedEx Corp. hide caption

itoggle caption Courtesy of FedEx Corp.

Growing demand for more fuel-efficient cars and trucks, like these 2009 Dodge Journey crossover vehicles, has helped drive down gasoline consumption in the U.S. David Zalubowski/AP hide caption

itoggle caption David Zalubowski/AP