The Trump administration took that formula’s figure, -0.5 for South Korea, and divided it by two to calculate the U.S. “discounted reciprocal” tariff rate. So, while South Korea imposes an effective tariff rate of .79 percent on U.S. goods, the reciprocal tariff rate the U.S. is imposing on South Korea is 25 percent.

A Trump administration official said the 10% baseline tariff rate was likely to stay in place for most nations as part of any negotiated trade deals.