History. 2 of 5: tariffs announced by the end of nine months (China on day 219, Ukraine 2001 on day 274). China's were dropped 22 days later and never took effect; the announcement is what counts.
Hunch. In July 2026 this same US trade office put tariffs of 25% on Brazil and 12.5% on Vietnam in two other investigations.
The 28 February market resolves YES if by the end of that day, Washington time, the trade office or the president has announced a decision to put tariffs on Vietnam in this investigation, even if they are later dropped or delayed and even if they start at 0%, while a deal, no penalty, a penalty that is not a tariff or only a proposal of tariffs with no decision on them is NO. The date of the action counts, with USTR releases and the Federal Register first, confirmed by Reuters, read through The Straits Times if Reuters does not open, and Reuters and AP as backup.
We looked for cases where US law forced the trade office to open an investigation, because it had just named that country a priority foreign country. We checked what it decided in the first six months. We found five such investigations from 1993 to 2013: Brazil, China, Paraguay and Ukraine twice.