Mainstream economists have been advocating for the marvellous effects of global trade for decades. Who needs these factory jobs anyway? We’ll be designing the robots and the nuclear rockets. Except that, no. It does not work like that. If you have the factories, sooner or later, you get the designers. If you don’t have the factories, you lose the expertise. Or you never get it. There aren’t that many people left in the Silicon Valley capable of working on silicon. You can design a chip from Cali...