President Trump is making a mistake with his plan to introduce 25 percent tariffs on steel imports and 10 percent tariffs on aluminum imports.

Doing so risks an economically damaging trade war with close allies like Canada, the European Union, and Japan. Moreover, if the president is serious about maintaining his tariffs for “a long time,” he’ll drive up the cost of car purchases and building projects. He’ll also reduce efficiency in high-end economic sectors where the U.S. enjoys a comparative advantage, such as airplane construction.