President Trump had the world’s attention yesterday when he unveiled his plan to rewire the global economic order by imposing expansive tariffs on nearly all of America’s trading partners. Today, the world responded.

The S&P 500 suffered its worst day since 2020, falling 4.8 percent. Some tech stocks like Apple and Amazon fell further. Markets in Asia and Europe pulled back. Business groups, trade experts, Democratic lawmakers and even a few Republicans denounced the tariffs.

Trump insisted this afternoon that the long-term payoff of the tariffs will be worth it. “The markets are going to boom,” he said. “The country is going to boom.”

Economists warned that the tariffs would raise prices for American consumers and lead employers to pull back on hiring. Some questioned how the strongest economy in the world faced a national “emergency” over its trade deficits. If the levies remain in place long enough, the economists said, the country’s resilient job market could begin to unravel.

Leaders in the E.U. and China, whose exports to the U.S. are set to face new double-digit fees, vowed to retaliate. President Emmanuel Macron of France called for a halt of investments in the U.S.

Canada placed a 25 percent tariff on American-made cars and trucks, in retaliation for a separate round of U.S. tariffs that went into effect today. Other leaders, including in Britain and Japan, were more restrained; Britain said that negotiations with the U.S. would continue.