In this bitter U.S. presidential campaign, one area of agreement unites the major candidates: trade. Bernie Sanders brags that he's opposed all recent trade agreements; Hillary Clinton now rejects the Trans-Pacific Partnership, President Barack Obama's signature trade success that she once supported; and Donald Trump blames incompetent U.S. trade negotiators for devastating job losses to China that might be cured by a 45 percent tariff on Chinese imports.

You should take all this with a boulder of salt.

True, a flood of Chinese imports over the past 15 years has cost hordes of U.S. jobs. In a recent paper, three respected economists — David Autor of the Massachusetts Institute of Technology, David Dorn of the University of Zurich and Gordon Hanson of the University of California, San Diego — estimated the loss of manufacturing jobs at 985,000 from 1999 to 2011.