Stocks sag for a third day

Investors second-guessing the strength of company results this week found more reasons to do so Thursday. Disappointing earnings and outlooks from big companies including American Express, Caterpillar and 3M helped drag stocks lower for a third day in a row.

The losing streak nudged the Dow Jones industrial average into negative territory for the year. The Dow slid 119.12 points Tuesday, or 0.7 percent, to close at 17,731.92.

The Standard & Poor's 500 index lost 12 points, or 0.6 percent, to 2,102.15. Utilities and materials stocks fell the most among the 10 industry groups on the index.

The Nasdaq composite declined 25.36 points, or 0.5 percent, to 5,146.41. The tech-focused index, which hit a high Monday, remains the best-performing index for the year, up 8.7 percent compared with 2.1 percent for the S&P 500.

Bond prices rose as investors shifted money from stocks. The yield on the 10-year Treasury note fell to 2.27 percent.

Though companies have mostly reported better-than-anticipated profits, many have fallen short when it comes to revenue. Others have issued cautious outlooks, citing the strength of the dollar, a slowing economy in China or falling oil prices.

What investors need to push stocks higher again is "true revenue growth from the corporate sector, which we just haven't seen," said Randy Frederick, managing director of trading and derivatives at Charles Schwab & Co.

American Express, Caterpillar and 3M all released weaker-than-expected results. American Express fell $1.98, or 2.5 percent, to $77.01. Caterpillar lost $2.88, or 3.6 percent, to $76.88, while 3M declined $5.91, or 3.8 percent, to $149.50.

Traders bid up shares in companies that delivered strong results. General Motors rose 4 percent after second-quarter earnings handily beat financial analysts' forecasts. Southwest Airlines turned in its ninth straight quarter of record earnings late Wednesday, and its stock also rose 4 percent Thursday.

Amazon jumped 15 percent in after-hours trading following better-than-expected earnings.

Roughly one-third of the companies in the S&P 500 have reported earnings so far. About 73 percent of them have delivered results that beat Wall Street estimates, according to S&P Capital IQ. But in many cases, companies are growing earnings by cutting expenses or buying back shares, Frederick said.

In energy-futures trading, benchmark U.S. crude fell 74 cents to close at $48.45 a barrel in New York. Brent crude, a benchmark for international oils used by many U.S. refineries, fell 86 cents Thursday to close at $55.27 in London.

Wholesale gasoline fell 1.6 cents to close at $1.852 a gallon. Heating oil fell 1.7 cents to $1.655 a gallon. Natural gas fell 8.1 cents to $2.816 per 1,000 cubic feet.

In metals trading, gold rose $2.60 to $1,094.10 an ounce. Silver gave up 3 cents to end at $14.68 an ounce. Copper fell 5 cents, to $2.39 a pound.