How, one might ask, is this possible, given Trump’s rhetoric, his determination to move against China with a 45 percent tariff? There’s a global macroeconomic variable that Trump left out of his calculus, and that’s America’s exchange rate—not just with China, but with the entire world. If America’s exchange rate increases, our exports become more expensive, and imports become cheaper—Italian designer clothing for the 1 percent and Indian and Bangladeshi clothing for the 99 percent.

Higher interest rates normally result in a higher exchange rate. But what happens if Trump does build his wall with Mexico, repeals NAFTA, imposes 45 percent tariffs against China, and labels China a foreign-exchange-rate manipulator? One of his advisers should have told him that China has been intervening in its exchange rate to prevent it from falling. If China stopped intervening, its exchange rate would fall—and our imports from China would increase. If it reduced restrictions on its citizens investing abroad, it would fall even more. If Trump imposes new tariffs on China, production of clothing and textiles won’t shift back to the U.S.; it will just move to elsewhere in the developing world. A few hi-tech companies might start producing goods in the U.S., but the sad news is that the jobs will be few and they will be hi-tech—not the jobs promised for the dislocated workers of the Rust Belt. And again, Trump will be foiled by the exchange rate: the higher tariff will result in a depreciation in China’s exchange rate, partially undoing any hoped-for benefits.

If Trump builds his new wall with Mexico, America’s car manufacturers will find themselves in an even tougher place than they are now. Without cheap car parts, they become un-competitive, both at home and abroad. The net result may be a loss of jobs, not more jobs. This is just another example of the jolt awaiting Trump: the world is a more complicated place than his rhetoric allows.

The real danger, however, is that Trump is edging America towards a trade war, a war in which we—and the rest of the world—are all likely to be losers. One of the oldest principles in economics is that of comparative advantage—if each country produces the goods in which they have a comparative advantage, each country will be better off. During the past few decades there was a bipartisan failure in not recognizing that even if the country as a whole is benefitting from trade, some groups may lose out—but the fault lies especially with the Republicans, who resisted any form of assistance to those whose jobs were lost as a result. That said, cutting off trade will result in a weakening of overall G.D.P.

But matters are worse: markets on their own are not good at making smooth adjustments, and learning to live without imports, or to live with much higher prices for imports, will not be easy. More jobs will be lost as the country loses comparative advantage across a wide swath of products. Without access to competitive imports, our exports themselves can’t compete. American workers will again lose twice: first because of the loss of jobs, and second, because of the higher prices for consumer goods.

American workers may be deceived by Trump’s blustering; and they may trust that our governmental institutions will prevent him from doing anything totally irresponsible. But foreign governments are likely to be less trusting—and less forgiving. They may resort to international laws and agreements that we have signed—and from which we can disengage ourselves only slowly, and at significant cost.

For instance, the United States pushed other countries to agree to a provision in trade agreements calling for “countervailing duties”: if a country provides a subsidy to a firm—either directly or indirectly, through the tax system—then any of our trading partners can impose an offsetting “duty” or tariff. Providing a subsidy was precisely what Trump did with his deal to keep Carrier/United Technologies deals in Indiana. That is what the U.S. did with the entire banking system, in the form of a massive bailout. It is what Washington did with the auto industry. Other countries have so far looked the other way. But if the U.S. starts playing “tough,” so can they. In fact, the U.S. has been brought before trade tribunals on charges of violating trade agreements 129 times in the past 20 years. But Trump promises to usher in a new era—not in fighting for our rights, but in violating international trade law.