A wave of late selling pummeled U.S. stocks Friday and pushed the market to its worst week in four years.
The dismal start to the new year comes as investors worry that China's huge economy is slowing down. That has helped send the price of oil plunging to its lowest level since 2004, the latest blow to U.S. energy companies.
Industrial and technology companies such as Boeing and Apple that do a lot of business in China have also fallen sharply this week. Mining companies such as Freeport-McMoRan plunged as copper prices have fallen. China is a major importer of copper.
Stocks started the day higher, driven in part by news of an encouraging burst in hiring last...