Stocks ended mixed on Wednesday following a volatile session in which reports that Moody's may lower the credit ratings of two key bond insurers overshadowed some positive U.S. economic news and lower oil prices. Stocks opened lower but rallied after a report showed moderate expansion in the U.S. service sector. The three major indexes stayed in positive territory for most of the session as oil prices declined and shares of Lehman Brothers, which were battered by credit concerns in recent sessions, rose following an upgrade by Merrill Lynch. But stocks faced pressure later in the day after ratings agency Moody's placed bond insurers MBIA and Ambac on review for a possible downgrade o their credit ratings. Wall Street sees a potential downgrade of the bond insurers' ratings as a sign that the credit crisis is continuing and that the financial-services sector has further to fall. In economic news, the Institute for Supply Management said its service-sector index for May fell to 51.7 from 52.0 in April. A reading above 50 indicates growth in the sector. In a second report, the government said first-quarter productivity was revised to a gain of 2.6 percent from an initial estimate of 2.2 percent. Light sweet crude oil for July delivery fell $2.01 to $122.30 a barrel on the New York Mercantile Exchange, following the weekly U.S. petroleum inventory report which showed a bigger-than-expected rise in gasoline supplies and a surprising decline in crude inventories. U.S. retail gasoline prices rose to their 27th record high in 28 days. The Dow Jones industrial average fell 12.37, or 0.1 percent, to 12,390.48. The broader Standard & Poor's 500 index was virtually unchanged, falling 0.45 to 1,377.20. The technology-heavy Nasdaq composite index rose 22.66, or 0.9 percent, to 2,503.14. The New York Stock Exchange composite index fell 49.24 to 9,212.76. The American Stock Exchange composite index fell 8.96 to 2,331.42. And the Russell 2000 index rose 4.71 to 743.71.
