Was Apple’s Warning a Surprise? Not to Its Suppliers

For the past two months Apple’s suppliers — the firms that make the parts inside iPhones — have issued sales warnings that have eroded the company’s shares.

On Thursday, it was Apple’s turn. Late Wednesday it reduced its revenue forecast for its most recent quarter because of a significant slowdown in iPhone sales in China.

Apple’s stock fell 10 percent on Thursday, r its worst one-day slide in six years. But the warning also rippled across its many suppliers.

The chip makers Micron Technology and Advanced Micro Devices fell 5 percent and 9 percent. Qorvo, a maker of radio frequency chips, and Cirrus Logic, which supplies audio chips for the iPhone, dropped 9 percent.i

Lumentum, which supplies optical components for the iPhone, slid 8 percent. AMS, a maker of light sensors for smartphones, tumbled more than 20 percent.

Since the iPhone was introduced in 2007, the market for mobile phones has become saturated. Even before Apple’s warning — its first in 16 years — investors had started to grow worried about the company’s ability to sell more phones.

That’s partly because Qorvo, Cirrus Logic, Lumentum and AMS had all already cut their revenue forecasts for the most recent quarter late last year. Though none of the companies mentioned Apple, the tech giant is the largest customer for each.

Those announcements weighed heavily on Apple’s stock. Over a three-day period in mid-November, Apple’s stock fell 9 percent after the warnings of Qorvo, Lumentum and AMS.