I N ITS SCOPE and severity, the trade war took markets by surprise. On April 3rd, the day after President Donald Trump laid out an unprecedented array of tariffs, the Russell 3000, one of the broadest measures of the American stockmarket,

President Trump’s new tariff regime imposes a 10% blanket duty on all U.S. imports, with targeted rates up to 49% on select countries, sparking fears of a global trade war.

For decades, global commerce abided by tariff rates agreed to by the U.S. and 122 other countries during the 1980s and 1990s. On Wednesday, Trump detonated that arrangement, saying that other countries had exploited the system and “ripped off’’ the United States for years, causing its once-mighty manufacturing base to shrink.