Plunging markets are normally unnerving because they reveal how quickly sober-minded investors can give in to terror. Just now the scariest thing is how rational those scrambling to sell appear. Share prices around the world have been cratering since Donald Trump announced his latest and biggest suite of tariffs on April 2nd. Although many market participants have held out hope that the new barriers would be swiftly lowered, perhaps after Mr Trump had used them to extract concessions from trading partners, it now looks increasingly likely that America’s president really means it. Indeed, on April 7th he announced additional tariffs of 50% on China, unless Xi Jinping withdraws his retaliatory levies.