The White House on Monday granted Europe, Mexico and Canada a reprieve until June 1 on U.S. steel and aluminum tariffs, which is better than imposing these border taxes on consumers and businesses. But if President Trump wants to understand the economic risks of his trade protectionism, he should look at Tuesday’s decline in the Institute for Supply Management’s monthly manufacturing gauge.
The measure fell to 57.3, still healthy but down two points from a nearly 14-year high in February. Tim Fiore, who supervises the ISM...