The new year is off to a rocky start on Wall Street as a revenue warning from Apple sent U.S. stocks plummeting Thursday.

The Dow fell 660 points, while Apple shares plunged nearly 10 percent on the heels of the company’s announcement that it would miss sales targets for the quarter ended Dec. 29. The tech company’s shares are among the most widely held in the world, but the bad news also stoked growing fears across a wide swath of industries, including retail and manufacturing, about a global economic slowdown and the impact of the ongoing U.S.-China trade war.

In a letter to investors published after the market close on Wednesday, Apple CEO Tim Cook placed much of the blame for the disappointing results on sluggish sales in China.

“While we anticipated some challenges in key emerging markets, we did not foresee the magnitude of the economic deceleration, particularly in greater China,” wrote Cook. “In fact, most of our revenue shortfall to our guidance, and over 100 percent of our year-over-year worldwide revenue decline, occurred in greater China across iPhone, Mac and iPad.”

The health of the Chinese consumer is of chief concern to global brands who are looking to the region as a growth opportunity, just as the health of its manufacturing sector is important to the many U.S. companies in the footwear industry and beyond that rely on it as a sourcing hub. Last month, China’s National Bureau of Statistics revealed that retail sales growth slowed to 8.1 percent in November, the slowest pace since 2003, fueling investor anxieties throughout the luxury sector.

With less than two months left before President Trump’s trade war truce with China reaches its deadline — and billions of dollars worth of tariffs already in effect — tensions between the two countries are running high.

In 2019, it will become more clear about which companies will ultimately bear the brunt of the economic uncertainty.

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