On a grey afternoon outside the White House, President Donald Trump promised that his tariff plan would “Make America Wealthy Again”. The world’s financial markets took a different view. Investors were shocked by the height and breadth of the new tariffs. According to Evercore ISI, a research firm, the new levies will raise America’s effective tariff rate from about 2% to 24%, the highest for over a century. It was, as Mr Trump said, a “historic” day.