(AP) -- Major U.S. stock indexes shifted lower in midday trading Tuesday after spending much of the morning wavering between small gains and losses. Investors were weighing the latest batch of company earnings news and looking ahead to the beginning on Wednesday of two days of testimony before Congress by Federal Reserve Chair Janet Yellen. European markets fell following steep losses in Japan.
KEEPING SCORE: The Dow Jones industrial average was down 82 points, or 0.5 percent, to 15,944 as of 12:18 p.m. Eastern Time. The Standard & Poor's 500 slipped eight points, or 0.5 percent, to 1,844. The Nasdaq composite fell 17 points, or 0.4 percent, to 4,266. Stocks posted steep slides Monday and Friday.
THE QUOTE: "The market has been trying to define a direction, leadership," said Quincy Krosby, market strategist for Prudential Financial. "But the pockets of uncertainty continue. That's part of what's holding the market back."
SECTOR TALLY: Five of the 10 sectors in the S&P 500 index moved lower, with energy and telecommunications services stocks posting the biggest decliners. Materials stocks led the gainers.
SALES CONCERNS: Viacom slumped 15.5 percent after the owner of Nickelodeon, MTV, Comedy Central and Paramount Pictures reported lower revenue for its latest quarter. The stock slid $6.48 to $35.37.
BAD FLICK: Twenty-First Century Fox fell 2.7 percent after the film and television production company reported quarterly revenue that fell short of analysts' estimates. The stock shed 66 cents to $23.93.
GOOD GRIP: Goodyear Tire & Rubber climbed 5.5 percent after its latest quarterly earnings easily beat Wall Street's forecasts. The stock rose $1.45 to $27.79.
RIDING HIGH: Martin Marietta Materials vaulted 8.2 percent after the construction materials company reported a sharp increase in earnings. The stock was one of the biggest gainers in the S&P 500 index, climbing $9.61 to $127.46.
ROUGH GOING: Stock markets have endured a torrid start to the year as investors have fretted over a number of issues, including the fall in the price of oil to multi-year lows, a slowdown in China and whether many parts of the global economy will fall into recession and suffer a debilitating period of deflation, or falling prices. Global equities have now lost about $6 trillion since the start of the year. In January, that was largely due to worries over the slowdown in China and the slump in the price of oil.
EYES ON THE FED: Yellen is scheduled to addresses Congress over two days Wednesday. Yellen will outline the central bank's outlook on the economy. Investors will be watching for hints about when the Fed will make its next move to raise its key interest rate. Most analysts and investors think the Fed will raise rates fewer than four times this year, if at all.
EUROPEAN MARKETS: Stocks managed to eke out early gains in Europe before succumbing to another bout of selling. The FTSE 100 index of leading British shares was down 1 percent, while Germany's DAX fell 1.1 percent. The CAC-40 in France was 1.7 percent lower.
ASIA'S DAY: Japan's Nikkei index tumbled 5.4 percent and the interest rate on the country's benchmark bond dropped into negative territory for the first time. The yields on Japan's bonds have been low for years as the country kept its interest rates at or near zero.
ENERGY: The International Energy Agency, which advises countries on energy policy, said oil prices will continue to come under pressure as supply is set to outpace demand this year. After heavy losses Monday, benchmark U.S. crude oil was down 81 cents, or 2.7 percent, to $28.88 a barrel in New York. Brent crude, a benchmark for international oils, was down $1.54, or 4.7 percent, to $31.33 a barrel in London.
BONDS AND CURRENCIES: Bond prices rose. The yield on the 10-year Treasury note fell to 1.73 percent from 1.75 percent late Monday. The dollar was down at 114.85 yen from 115.58 yen. As recently as the end of January, the dollar was trading above 121 yen. The euro up $1.1327 from $1.1186.