THIS month will mark a major milestone in the global economic calendar: it will herald the end of three rounds of quantitative easing (QE) by the US Federal Reserve. While this has been a long-anticipated event, its consequences are uncertain, and economies - particularly in Asia - should brace for the possibility that they will not all be pleasant.

First launched in 2009, QE has been a marathon exercise in unorthodox monetary policy, under which the Fed maintained interest rates at close to zero for five years and launched a massive programme of bond purchases to the tune of more than US$4 trillion in total. Those purchases will stop by the end of this month.

Economists are divided on how effective QE has been in improving economic conditions. The US economy's recovery has been excruciatingly slow, and unemployment was stubbornly high for at least three years. Despite low interest rates, bank borrowing remained weak, and companies preferred to accumulated cash than to invest. But on the plus side, even the critics of QE would concede that the policy prevented the great recession of 2008-09 from turning into a depression. It also contributed to an asset price surge, including in emerging economies.