"With asset prices so frothy, it is understandable that central banks would be wary of beginning to taper monthly bond purchases before it is clear that inflation has taken off. But they would do well to recognize that prolonging quantitative easing implies significant risks, too."

"With growth so uncertain, it is understandable that central banks would be wary of beginning to taper monthly bond purchases before it is clear that inflation has taken off. But they would do well to recognize that prolonging quantitative easing implies significant risks, too."