On February 13th Donald Trump announced he had decided, for what he later called “purposes of fairness”, to employ reciprocal tariffs. When the levies will go into effect, and how they will apply, is uncertain.

If the US genuinely tries to close its overall deficit with big tariffs all round, it will cause a crunching recession. If Trump discriminates between trading partners, the heavily tariffed ones can nip through the side door of those who escaped more lightly.

President Donald Trump is taking his enthusiasm for tariffs to a new level. In his latest move, he has announced a policy of "reciprocal" tariffs that would tax imports from other countries at the same rate they tax imports from America.