Manufacturing jobs continue to leave the country, resulting in many workers without jobs and without hope.

During his campaign, President Trump promised to keep manufacturing jobs in the U.S. His first attempt to demonstrate this pledge was to get Carrier to keep several hundred jobs from moving from Indiana to Mexico. But Carrier has now cut several of those Indiana jobs, and another Indiana company, Rexnord, will be closing its Indianapolis plant and moving its operation to Mexico.

The blue-collar workers who have lost their jobs don’t have the skills to find work in the new economy. And jobs that in the past were handled by people are now being done by robots and advanced computers.

“This is a runaway train,” says Anthony Carnevale, director of the Georgetown University Center on Education and Workforce. “In the end, technology and global markets improve productivity and benefit all of us. Sadly, it hurts some of us even more.”

Despite this, some manufacturers are still optimistic. The U.S. economy has added 41,000 manufacturing jobs since February, and large firms such as GM and Hyundai have announced new investments in U.S. factories, according to the May 29 issue of Time magazine.

But many economists are far more skeptical, citing the fact that the nature of work—and manufacturing specifically—has fundamentally changed. Tax incentives to keep manufacturing jobs in America won’t stop companies from taking advantage of the cost savings and efficiencies of robotics and computer technology. Economists view these kinds of government policies as empty promises. “Those are not the policy solutions of the future,” John Van Reenen, a professor of applied economics at MIT, told Time. “Those are policy failures of the past.”

That leaves blue-collar workers in areas where manufacturing plants are closing with few opportunities to find work unless they are able to gain new skills.