Equity markets have wobbled three times this year in the face of disappointing economic news, not to mention the political turmoil in the Middle East and Ukraine. But those tumbles have so far been modest by the standards of past bear markets. Recent experience has taught many investors that good news can equal bad news: the more uncertain the outlook, the more supportive central banks are likely to be. The Fed may be reluctant to tighten monetary policy until the recovery is better established (markets are not now expecting a rate rise until March 2016) and the European Central Bank may feel obliged to loosen policy further.