FORTUNE -- Not long ago, leaders of emerging economies thought the U.S. Federal Reserve's easy money policies aimed at nursing the American economy back to health might also destroy the rest of the world. But as the U.S. economy slowly improves, some countries now worry that the Fed's stimulus may be coming to an end.
This not only says a lot about the Fed's biggest experiment in monetary policy since the Great Depression, but it also highlights that no matter what the Fed does, some central bankers won't be happy.
Fed Chairman Ben Bernanke shocked markets in May when he said the central bank could slow down its $85 billion monthly asset purchases if the U.S. economy continues to improve. That's a big if, given that unemployment, while it has improved, is still relatively high. And if the job market all of a sudden falls back to trouble territory, the Fed could increase its monthly bond purchases, as Bernanke reaffirmed Wednesday.
Before slipping Tuesday and Wednesday, yields on U.S. Treasuries had risen sharply over the past few weeks as bond investors fled the market.
Investors aren't the only ones reacting in big ways, though: On Tuesday, South Korea's finance minister warned emerging economies might be forced to cut imports from the U.S. if the Fed isn't careful in unwinding QE. This makes sense -- if the value of the U.S. dollar rises, which it has done for several months now and likely will continue, whatever America sells to the rest of the world becomes more expensive.
What's surprising, though, is how quickly the tone has shifted. A year or so ago, emerging market exporters were still battling rising exchange rates. In 2010, Brazil blamed Western policymakers, particularly the U.S., for waging "currency wars" by flooding the world with cheap money. They thought the value of the U.S. dollar would spiral down to oblivion and cause currencies across emerging markets to rise to levels that would make exports more expensive and their countries less competitive.
Three years later, the currency wars Brazilian Finance Minister Guido Mantega and others warned about haven't emerged. Widespread currency devaluation never set off a global economic disaster. And now much of the money that investors poured into emerging economies after the start of the Fed's QE is now leaving those countries in anticipation of its end. Last week, Turkey tightened policy in efforts to pull the lira off record lows. It wouldn't be surprising if other economies follow.
And contrary to what some had thought, QE hasn't destroyed the U.S. Dollar. After more than a decade of decline, the greenback has risen by about 7% since late 2011, and the rise will likely continue if the economy improves further.
South Korea may worry about a fall in U.S. imports, but those concerns say a lot about the way emerging economies have come to not only embrace, but also to rely on QE.
"QE was supposed to make the U.S. economy stronger," says James Wilcox, professor at Berkley University's Haas School of Business. "With more personal income in the U.S. we would buy more Japanese cars, hydrated beef from Latin America, and so on, and that would help exports across emerging economies."
So as much as emerging economies have criticized QE, it's harder for them to see how their exports might grow without it.
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