If Trump announces 25% steel and aluminum general tariffs today, he will be repeating what he did in early 2017, with no positive effect whatsoever. The main exporters now are the same as then: Canada first, Europe, Mexico. There are plenty of records of it: Imports fell in 2017-18; but domestic consumption of steel fell by slightly more, so U.S. steel production fell slightly from about 100 million tons. Steel prices rose. That production is somewhat lower now than it was in 2015, for example. China still produces more than half the world’s steel. The result was similar for aluminum.