Yahoo Finance analysis indicates that Donald Trump's tariff policy has repeatedly caused multi-trillion-dollar stock market swings since early 2025, with markets still struggling to price in his next move. The analysis highlights that U.S. tariff policy has changed over 50 times since January 2025, often announced via social media posts, leading to significant volatility. For example, on April 3, 2025, the S&P 500 fell 4.8%, Nike crashed 14%, and Apple declined 9% due to new tariffs. Later, on October 10, a threatened 100% tariff on Chinese goods caused roughly $2 trillion in American stock market value to vanish that afternoon, though these increases were later scrapped. The market's difficulty stems from the unpredictable nature of these announcements, which are often part of a bargaining process and can be waived.