On April 5, The Washington Post reported that after Trump took office as U.S. president, the administration's economic workers began a difficult task: set tariff rates for dozens of countries to meet his campaign promise to set "peer-to-peer" trade barriers.

After weeks of work, assistants from several government agencies have developed a list of options covering a variety of trade practices. However, Trump personally chose a formula based on two simple variables. Sources said it was unclear who proposed the option, but it had some striking similarities to the approach published by Navarro, a tough economic adviser during Trump’s first administration.

The market fell sharply on Wednesday after tariff measures were issued, a rough calculation was ridiculed by economists. The report also said that after late-night discussions on Tuesday, Trump did not decide on his final plan until around 1 p.m. Wednesday—less than three hours after his announcement in the Rose Garden.