Tariffs. Protectionism. Economic nationalism. Taxing trade. Putting up barriers to doing business across borders. Few things unite economists. But the belief that all of the above make people everywhere less prosperous has long been one of the few things that almost everyone in the dismal science believes.  The president-elect of the United States is not an economist. Donald J Trump, since his emergence as a public figure in the 1980s, has claimed the US is being ripped off by its trading partners around the world. That would certainly not be the view of anyone who has ever seen American trade…