Companies shifted low-skill jobs to China in the 2000s because American workers couldn’t compete with Chinese workers earning around $1 an hour. Now China itself is losing low-wage manufacturing jobs to poorer countries such as Bangladesh and Vietnam.

If America tried to block foreign-made products and make everything at home, prices would skyrocket and foreign countries would likely retaliate by blocking U.S. goods from their countries. “You can’t turn back the clock,” Blinder says.

But there’s an even bigger problem for those who want to restore U.S. manufacturing employment (now 12.3 million) to its 1979 peak of 19.6 million: Technology has taken many of those jobs for good. Today’s high-tech factories employ a fraction of the workers they used to. General Motors, for example, employed 600,000 in the 1970s. It has 216,000 now — and sells more cars than ever.

“No matter who becomes president,” says economist David Autor of the Massachusetts Institute of Technology, “I cannot foresee a scenario where 5 million additional manufacturing jobs … reappear in the U.S. in the decades ahead.”