The trade war between the United States and China is now in full swing. U.S. President Donald Trump has retaliated against Beijing’s own retaliatory tariffs, imposing an additional 50 percent levy on China on Tuesday. Companies importing goods from China will now have to pay a tariff worth more than the product itself. Lost in the week of bruising trade combat is a new set of Chinese constraints on all exports of seven so-called rare earths — a group of 17 elements that are used in everyt