SO BEGINS Donald Trump’s tariff roller-coaster, sure to be a stomach-churning ride for the global economy. He started his first day in office with an unexpected show of restraint: rather than slapping hefty new tariffs on other countries, he instead issued a presidential memorandum calling for a review of unfair trade practices. It seemed to be a measured start for Mr Trump—at least on the protectionist front, if not his wider programme—prompting relief in government offices and on trading floors around the world. Foreign currencies and stocks rallied.