The official presidential proclamation published on the White House website is a primary legal document announcing the imposition of a temporary import surcharge and is the most authoritative evidence confirming a new global tariff policy. It explicitly specifies a 15% rate, establishing that the United States, under Donald Trump, implemented a global tariff increase to that level. This source carries the highest authority and directly supports the claim. Secondary confirmation from contemporaneous Reuters reporting corroborates that Trump publicly stated his intention to impose a 15% global tariff, aligning with the official document. Market-related coverage from CNBC mentions short-term volatility and trader reactions in U.S. stock futures following the announcement, suggesting at least a temporary decline. There is no credible evidence contradicting the existence of the 15% tariff or that stock futures fell immediately afterward. Some Treasury and congressional materials provide legal or administrative context but do not contradict these findings. Therefore, the combined weight of an official proclamation and consistent media reporting makes the statement highly likely to be true, with only minor uncertainty about the exact duration and magnitude of the stock futures decline.