With a few strokes of a big black marker, Trump signed an executive order on Thursday to start up new tariffs on dozens of countries. While the move follows last-minute deals with a handful of partners, economist Niclas Poitiers told The World’s Host Carolyn Beeler that those agreements are unlikely to last and tariffs have only sowed more uncertainty in the global economy. Poitiers is a research fellow at Bruegel, an economics think tank based in Brussels.