How Tariffs Affect Stock Markets in 2026
Trade policy remains one of the most powerful forces shaping stock markets in 2026. On February 20, the U.S. Supreme Court struck down President Trump's sweeping "reciprocal" tariffs in a landmark 6-3 decision, ruling that the International Emergency Economic Powers Act does not authorize the president to impose tariffs. Within hours, Trump announced a new global 10% tariff — then raised it to 15% days later — while courts set the first major tariff refund deadline for importers who had overpaid under the now-invalidated regime. The tariff saga is now colliding with a new geopolitical crisis. U.S. and Israeli strikes on Iran in late February 2026 have disrupted shipping near the Strait of Hormuz, through which roughly 20% of global oil passes daily. Three ships were attacked near the strait on March 1, raising fears of sustained trade route disruption that could compound the inflationary effects of existing tariffs. This guide explains what tariffs are, how they ripple through the economy to affect specific sectors and stocks, and what investors should watch as trade policy intersects with geopolitical risk. Whether you're evaluating Nike's supply chain exposure, Walmart's import costs, or Boeing's defense positioning, understanding tariff mechanics is essential for navigating today's markets.