ON March 8, Donald Trump made an announcement which according to many has the potential of starting a global trade war. He announced that the US would be raising tariffs on imported steel by 25 per cent and tariffs on imported aluminium by 10 per cent.Now, the WTO allows tariffs under certain circumstances, against, for instance, some country that is “unfairly” subsidising its exports, or is dumping its goods, which means charging higher prices on the domestic market for the same goods that are sold cheap in the export market.