Oxford, England — One of Donald Trump’s most misleading campaign themes is that Mexico is stealing U.S. jobs, and that Washington should renegotiate or scrap its free trade deal with Mexico to prevent even larger job losses. In reality, what’s threatening U.S. jobs isn’t Mexico, but automation.

I thought a lot about Trump’s deceptive trade proposals this week while visiting Oxford University to interview the co-author of a much-cited Oxford-Martin School study on the future of employment. The study says 47 percent of U.S. jobs are at risk of disappearing over the next 20 years because of automation.

Carl Benedikt Frey and Michael A. Osborne looked at 702 jobs listed by the U.S. Department of Labor and ranked them according to their likelihood of being replaced by computer programs and robots. Since the study’s publication in late 2013, its conclusions “have only been further validated,” Osborn told me.

In essence, almost every job that is mechanical, or follows a physical or intellectual routine, is likely to disappear in the near future, the authors say.

Among the jobs that will be most threatened are those of factory workers, waiters, salespeople (who are already being replaced by internet shopping and robotic telemarketers), secretaries, and many banking and legal jobs.

Critics point out that there have been similarly alarming forecasts about a jobless future since the 1760-1840 Industrial Revolution, and that — until now — such fears have been proven wrong. However, many argue that technology is advancing at such an unprecedented speed, it is now destroying more jobs than can be created.

None of this seems to matter to Trump, the “I love the uneducated” presumptive Republican candidate who is fooling anxious workers in U.S. industrial states into thinking that scrapping the free trade deal with Mexico and imposing a 35 percent tax on Mexican imports would help create U.S. jobs.

Aside from the fact that Trump’s proposals are based on deceptive data — he neglects to point out, for instance, that up to 6 million U.S. jobs depend on free trade with Mexico, according to the U.S. Chamber of Commerce — his claim that offshored manufacturing jobs will come back to Ohio or Wisconsin is a fantasy.

“No country has become prosperous by protecting and conserving employment in the old and declining industries,” Frey told me in a recent interview. “At the end of the day, where industrial jobs are disappearing, the task of policymakers is not to bring back old jobs, but to create new employment opportunities in new types of industries.”

He added, “What would help the United States would be to, first of all, make sure that low-skilled workers that have been deprived of work in manufacturing industries are trained in a way that they can work in new types of industries. And second, invest in new technology and new industries to create new types of jobs.”

My opinion: I fully agree. Trump — and to a lesser extent presumptive Democratic candidate Hillary Clinton, in her quest for support from her party’s left wing — are deceiving U.S. voters by putting the blame of lost U.S. jobs and declining wages on Mexico, or China.

If the United States scrapped its free trade deals and slapped high tariffs on imported goods, U.S. consumers would have to pay much more for almost everything — cars, cell phones, clothing, you name it — and other countries would start a trade war that could depress the world economy, much like what happened in the Great Depression of the 1930s.

And if Trump kept his promise of punishing U.S. companies that keep manufacturing plants in Mexico or China to remain competitive, these companies would not repatriate those jobs to the United States. They would replace them with robots, which are increasingly cheaper and more sophisticated, and don’t ask for wage increases.

The real discussion in the U.S. presidential campaign should not be how to avoid U.S. jobs from going to Mexico, or China. It should be about how to better educate our youth and retrain U.S. workers, so that they can have more and better jobs to replace those that will inexorably disappear because of offshoring or automation.

— Andres Oppenheimer is a Latin America correspondent for the Miami Herald.