Federal Reserve Bank Chair Janet Yellen holds a news conference after the central bank announced its first rate increase in more than 9 years. Chip Somodevilla/Getty Images hide caption

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Plummeting energy prices have hit the junk bond market hard, making investors worry that weaker oil and gas companies won't be able to pay back money they've borrowed. Above, a customer pumps gasoline in Pembroke, Mass. Stephan Savoia/AP hide caption

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April Thompson makes a purchase at Legacy Team Sales in Ocala, Fla., in September. Economists say October's surprisingly strong job growth will encourage the Federal Reserve to hike interest rates next month. So holiday shoppers may pay more for using credit cards. Doug Engle/Ocala Star-Banner/Landov hide caption

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A police officer keeps watch outside the Federal Reserve headquarters in Washington, D.C., where policymakers weighed whether to boost interest rates. Kevin Lamarque/Reuters/Landov hide caption

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Federal Reserve Chair Janet Yellen, speaking at a news conference in Washington on Thursday, said the U.S. economy has been performing well but the global outlook is more uncertain. Jacquelyn Martin/AP hide caption

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Federal Reserve Chair Janet Yellen testifies before the Senate Banking Committee in July. This week, Yellen and other policymakers are weighing the Fed's first rate increase in nine years. Susan Walsh/AP hide caption

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Federal Reserve Chair Janet Yellen and other policymakers will meet in Washington, D.C., this week to weigh a possible increase in interest rates. Manuel Balce Ceneta/AP hide caption

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Federal Reserve Vice Chairman Stanley Fischer speaks during a Board of Governors of the Federal Reserve System meeting in July. Manuel Balce Ceneta/AP hide caption

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