Wall Street Edges Lower - NYTimes.com Stocks traded lower on Wall Street on Wednesday as earnings season started with a warning from Alcoa about slower aluminum consumption, underscoring concerns about sluggish worldwide growth. Other large companies warned of slowed growth, including Chevron and the engine maker Cummins. The Standard & Poor's 500-stock index fell 0.6 percent in afternoon trading. The Dow Jones industrial average dropped 0.7 percent and the Nasdaq composite index lost 0.4 percent. Stronger demand from airplane and automobile producers helped Alcoa, the largest aluminum producer in the United States, to report third-quarter results that beat analysts" expectations, but its revenue warning hurt shares. Alcoa lost 1.6 percent. Lackluster growth in China, the world's second-largest economy, was expected to rein in corporate earnings in the third quarter and dent profit forecasts. China has been feeling the pinch of the debt crisis in the euro zone, a key trading partner. Earlier in the week, the World Bank cut its growth forecast for East Asia on concerns China's slowdown could last longer than expected. You've seen very cautionary earnings results and even forward guidance. Alcoa has good earnings, but their forward guidance is lackluster. It points to a slow China and slow global growth," said Richard Weeks, managing director at HighTower Advisors in Vienna, Va. Analysts predicted that third-quarter earnings of Wall Street's S.&P. 500 companies would fall 2.3 percent from the year-ago quarter, according to Thomson Reuters data. That would be the first drop in American quarterly earnings in three years. According to data through Tuesday, 94 companies in the benchmark S.&P. index have issued negative outlooks, compared with 22 positive, for a ratio of 4.3, the weakest showing since the third quarter of 2001. Going against general declines was Yum Brands, which gained 4.8 percent. The KFC parent company had raised its full-year outlook after sales in China held up despite that nation's cooling economy. The S.&P. 500 has fallen for three consecutive sessions on growing concerns about corporate profits, with the index closing on Thursday near the technical support level of 1,440 points. Chevron, the second-largest American oil company, dipped 3.1 percent after it warned third-quarter profit would be "substantially lower" than in the previous quarter as a hurricane and maintenance curbed its oil and gas output and a fire hit its refining arm. Cummins lowered its 2012 forecast for a second time this year, citing delays in customer spending caused by a weakening global economy, and said it would cut up to 1,500 jobs. Cummins shares dropped 2.6 percent. Earnings from warehouse chain Costco Wholesale were a bright spot; the company reported a 27 percent jump in fourth-quarter profit on higher sales and membership fees. Costco shares were up 3.6 percent. Coming on the heels of a 2013 profit forecast that was cut last month, FedEx said it plans to slash costs at its underperforming express airfreight and services divisions, with profit improvements of $1.7 billion planned at those operations over the next four years. Shares gained 4.7 percent.