The first is the gap between America, where growth is accelerating, and almost everywhere else, where it is slowing. In the late 1990s Larry Summers, then the US deputy treasury secretary, warned that the world economy was “flying on one engine”. For 2015 The Economist’s panel of forecasters expects 3% growth in America, compared with 1.1% in Japan and the euro area. China’s growth rate may fall to around 7%.