Former President Donald Trump blames the global trading system for inflicting a long list of ills on the American economy, including lost jobs, closed foreign markets and an overvalued dollar.

The remedy, he insists, is simple: tariffs.

Trump, the Republican nominee for president, has repeatedly said he would raise tariffs if elected. China, a geopolitical and economic rival, would face an additional 50% or 60% tariff on its exports to the United States. He has also floated the idea of a 10% surcharge on exports from the rest of the world.

Although smaller than the percentage proposed for Chinese exports, an across-the board tariff has the potential to deliver a much more devastating jolt to world trade, many economists warn.

Such a surcharge would not distinguish between rivals and allies, critical necessities and nonessentials, ailing industries and superstars, or countries adhering to trade treaties and those violating them.

Democrats have also embraced tariffs as a policy tool, but Vice President Kamala Harris, the Democratic nominee, has criticized Trump’s universal approach as inflationary.

Here is what you need to know about the idea of a universal tariff on all imports.

What is the historical precedent?

Trump’s broad-brush tariffs frequently evoke comparisons with the global trade war that the United States helped to initiate in the 1930s with the Smoot-Hawley tariffs passed by Congress. The Senate Historical Office has called that law “among the most catastrophic acts in congressional history.”

Would an across-the-board tariff make a good bargaining tool?

Trump has said he would dangle the threat of tariffs as a negotiating tactic to force concessions from trading partners.

“And man, is it good for negotiation,” Trump said of tariffs in an interview with Bloomberg Businessweek. “They would do anything.”

Yet during Trump’s term in office, some of the biggest U.S. trading partners responded to his tariffs with tariffs of their own, including the European Union, China, Canada, Mexico and India.

If Trump imposes a 10% surcharge on all imports, “each country, including Japan, will take retaliatory measures of the same degree,” said Shigeto Nagai, head of Japan economics at the advisory firm Oxford Economics.

That could result in the worst possible outcome for the United States and its allies, economists said: a combination of recession and higher inflation.

“Nobody is excited about a trade war,” said Kimberly Clausing, an economist at the Peterson Institute for International Economics, who served in the Treasury Department under President Joe Biden. “But nobody is excited about bullying from the Trump administration.”

What would be the economic consequence of a “tariff on everybody”?

The United States imported $427 billion worth of goods from China in 2023, Clausing said, while imports from the rest of the world totaled nearly $2.7 trillion. “So I would expect this to be a bigger shock, both to the U.S. economy but also abroad,” she said.

Trump’s 2018 tariffs on China caused a rebalancing of trade, the International Monetary Fund found. China exported more to other countries, and other countries exported more to the United States.

Trump and economists who support him have argued that tariffs would increase production at home, create high-paying jobs and decrease inflation. And, he says, it would bring in additional revenue.

Most economists, though, agree that the overall downsides outweigh the gains. Rounds of tit-for-tat tariffs would ultimately hurt every country by limiting trade, disrupting global supply chains, slowing growth and pushing up prices.