S&P 500 ends down after mostly negative week

Wall Street finished mostly lower on Friday, weighed down by Big Tech as investors digested the Federal Reserve's decision to end its pandemic-era stimulus faster.

All three main U.S. stock indexes ended with a decline for the week after the Fed on Wednesday signaled three quarter-percentage-point interest rate hikes by the end of 2022 to combat surging inflation.

Apple (AAPL.O), Microsoft (MSFT.O) and Alphabet (GOOGL.O) slipped for much of the session, weighing on the S&P 500 and Nasdaq.

Adding to uncertainty, Pfizer (PFE.N) said on Friday the pandemic could extend through next year. European countries geared up for further travel and social restrictions and a study warned that the rapidly spreading Omicron coronavirus variant was five times more likely to reinfect people than its predecessor, Delta. 

Traders also pointed to year-end tax selling and the simultaneous expiration of stock options, stock index futures and index options contracts - known as triple witching - as potential causes for volatility.

"It's a big options expiration day," said Joe Saluzzi, co-manager of trading at Themis Trading in Chatham, New Jersey. "And now you draw on top of that some Omicron, and you've got volatility, and I think it creates a lot of uncertainty amongst investors. Where are you going to position for the end of the year?" Heavyweight growth stocks including Nvidia (NVDA.O) and Microsoft have outperformed the broader market in 2021, while the Philadelphia SE Semiconductor index (.SOX) has surged about 35%. The benchmark S&P 500 index gained around 23% in the same period.

According to preliminary data, the S&P 500 (.SPX) lost 48.75 points, or 1.04%, to end at 4,619.92 points, while the Nasdaq Composite (.IXIC) lost 14.80 points, or 0.07%, to 15,165.63. The Dow Jones Industrial Average (.DJI) fell 532.14 points, or 1.48%, to 35,365.50.

The small-cap Russell 2000 index (.RUT) rallied after having fallen more than 10% from a record high in early November.

Oracle (ORCL.N) tumbled after the Wall Street Journal reported the enterprise software maker is in talks to buy electronic medical records company Cerner (CERN.O) in a deal that could be valued at $30 billion. Shares of Cerner surged. FedEx Corp (FDX.N) rose after the delivery firm reinstated its original fiscal 2022 forecast on Thursday, even as persistent labor woes chipped away profits.