President Trump has accused America’s trading partners of undermining the United States for decades, saying they have engaged in unfair trade practices to steal the country’s wealth and enrich their own economies.

He has set his sights on not only adversaries like China, but also traditional allies like Canada and Europe. And he has complained about a number of factors, including high tariffs that other countries charge American products, and persistent trade deficits the United States has with foreign countries. Mr. Trump has promised to correct this situation on Wednesday, when he announces expansive tariffs on foreign products that he says will level the playing field.

In some cases, there’s truth to the president’s claim that the United States offers its trading partners more favorable terms than it often gets in return. As a proponent of free markets, the United States has long been more open to trade than many countries globally.

That has encouraged the United States to rely on imports of many critical goods, like semiconductors and pharmaceuticals, instead of manufacturing them itself. And some countries do have tough trade barriers to U.S. exports, or economic policies that distort global markets — particularly China, which has flooded the world with manufactured goods.

Still, trade experts say that Mr. Trump’s claims include a heavy dose of exaggeration, as well as hypocrisy.

For example, Mr. Trump has singled out high tariff rates that countries charge on certain U.S. exports including Europe’s tax on cars and India’s levy on motorcycles. But the United States also has high tariff rates that it charges on certain imports, such as a 25 percent fee on light trucks. And Mr. Trump has lumped in friendly allies like Canada, which have some limits to U.S. exports outside a few sectors, with nations like China, which have extensive trade barriers.

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