Investors have been second-guessing the strength of company results this week and they found more reasons to do so Thursday.

Disappointing earnings and outlooks from several big companies, including American Express, Caterpillar and 3M, helped drag U.S. stocks lower for a third day in a row. The losing streak has nudged the Dow Jones industrial average into negative territory for the year.

While companies have mostly reported better-than-anticipated profits since the start of the month, 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. That’s giving investors reason to pause.

What investors need in order 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.

Amazon bucked the trend, jumping 15 percent in after-hours trading after better-than-expected earnings.

The Dow slid 119.12 points, or 0.7 percent, to 17,731.92. The average is now down 0.5 percent for the year.

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. It’s up 8.7 percent, compared with 2.1 percent for the S&P 500.

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

A slide in the price of oil deepened on concerns that global crude supplies continue to outpace demand. U.S. crude is below $50 a barrel.

Thursday’s stock market decline began early as investors sized up the latest earnings.

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 other companies that delivered strong results.

General Motors rose 4 percent after the automaker’s second-quarter earnings handily beat financial analysts’ forecasts. Southwest Airlines turned in its ninth straight quarter of record earnings late Wednesday. The stock also rose 4 percent.