SMM12 11: Trump's metal tariffs have proved to be a double-edged sword. Although domestic steel prices initially soared after the new tax was announced in March, they have fallen in recent months. The reason is that concerns about US steel exports have heightened trade tensions between the US and China, threatening global economic growth and demand for commodities. The same concern is weighing on producer stocks, with the S & P Supercomposite Steel Index) of 13 companies falling to its lowest level in nearly 18 months on Monday and sliding further into a bear market.