President Donald Trump just enacted a new wave of tariffs on dozens of America’s trading partners, marking a substantial escalation in ongoing trade tensions that could constitute the biggest change to the global economy in nearly a century.

Economics textbooks insist that stock prices reflect the future stream of a company’s profits on any given day. For all the brainpower devoted to these forecasts, however, they are essentially rough estimates of what may happen over the next twelve months and wild guesses about anything after that.

President Donald Trump’s sweeping new tariffs finally took effect on Thursday, slapping levies on dozens of countries and risking price increases for a host of everyday goods. Tariffs between 10% and 41% were applied to nearly 70 countries beginning at 12:01 a.m. Thursday, significantly expanding the reach of Trump’s confrontational trade policy.