The world’s central banks and the wave of unorthodox monetary policy may be offsetting what ought to be a boost to global growth from cheap oil, according to research by the International Monetary Fund. The IMF has hinted heavily that it will next month lower its 3.4 per cent growth forecast for the global economy with one of the main reasons being the failure of cheap oil to deliver a widely anticipated fillip to major economies. Just why that boost to growth from lower energy prices has not materialised has perplexed many economists. But in a new blog post published on Thursday that offers a preview of a deeper study to be released ahead of next month’s IMF/World Bank spring meetings in Washington, Maurice Obstfeld, the fund’s chief economist, offers a possible explanation that is likely to prompt plenty of debate. He also renews an IMF call for the world’s big economies to do more to stimulate demand and growth.