In 1971 John Connally, then the American treasury secretary, told his European counterparts that the dollar was “our currency, but your problem”. Over the following half-century the global economy has transformed, but Connally’s adage still rings true: even though the value of the dollar remains largely set by domestic developments in America, its swings almost always send ripples across the world. One such big swing may be on the cards, as the economic policies promised by Donald Trump, America’s president-elect, look set to turbocharge the greenback. That spells trouble for growth in the rest of the world.