U.S. stocks fell for a fifth day on Thursday, with the S&P 500 finishing below 2,000 for the first time in a month, as crude prices fell, large U.S. banks reporting disappointing results, and Switzerland's central bank unexpectedly gave up its minimum exchange rate.
"Central bankers were surprised today, and investors too, by the whole Swiss thing," Kim Forrest, senior equity analyst at Fort Pitt Capital, said.
"It foretells what happens next week, if they are going to massively do QE (quantitative easing), which is kind of what is indicated by the Swiss move today," said Forrest, who added that what remains unclear is "how forcibly (European Central Bank President Mario) Draghi is going to be able to do QE."
Bank of America dropped after the bank reported a 14 percent fall in quarterly profit; Citigroup also declined as it posted a slim fourth-quarter profit. Target shares rose after the discount retailer should it would discontinue operations in Canada.
"Bank earnings are a negative," Art Hogan, chief market strategist at Wunderlich Securities, said.
The CBOE Volatility Index, a measure of investor unease, rose 4 percent to 22.33.
A measure of manufacturing in the new York region climbed to 9.95, above estimates. Other reports had wholesale prices falling 0.3 percent in December, and a larger-than-expected number filing for jobless benefits last week, up by 19,000 to 316,000.