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After nearly five years of negative interest rates, the oldest central bank in the world has had enough.

Sweden's Riksbank hiked its key interest rate back to 0% on Thursday, becoming the first central bank to enter negative territory and then come back up amid growing concerns that harmful side effects are outweighing the benefits of such policies.

"It's part of a general unease about having rates in negative territory," David Oxley, senior Europe economist at Capital Economics, told me.

Background: Central bankers have conducted an unprecedented experiment since the 2008 financial crisis. To juice a sluggish global economic recovery, they've pushed interest rates to their lowest points in history. In Europe and Japan, rates have been in negative territory since 2014 and 2016, respectively. Sweden's main rate went negative in 2015.

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