The Trump administration’s section 232 tariffs on steel and aluminum imports are having their desired effect. Imports fell 17.6% year over year in April and by a further 5.7% in May, based on preliminary data. Yet, that only leaves imports at levels before the tariff review was launched in April 2017. Shipments may rise in the coming months after Canada and Mexico received exemptions from the tariffs in May. Most of the major steel and aluminum exporters to the U.S. have cut their shipments. Tenaris’ shipments fell 27.4% year over year in the year-to-date through May 31, w...