It seems like five minutes ago that America’s stockmarket was the only game in town. Prices were breaking records every other week; rivals around the world had been left behind. Now investors’ faith in the country’s exceptionalism has been shaken by a deteriorating outlook for economic growth and Donald Trump’s erratic protectionism (see chart 1). Indeed, on March 11th the president said that he would double new tariffs on Canadian aluminium and steel. Investors are therefore less willing to pay far higher multiples of underlying earnings for shares in American firms than for those listed elsewhere, a decision that had been justified by fatter profit margins and stronger growth prospects.