Most central banks have been easing policy since the start of the year and are set to do more, but it still isn’t clear whether that new activism, which has pushed stock markets to record highs, will help the global economy much. Several meet this week to set policy, including the U.S. Federal Reserve, the Bank of Japan and Sweden’s Riksbank, which all have turned to government bond purchases as stimulus after running out of interest rates to cut. The Fed shut its quantitative easing (QE) program just over six months ago.