U.S. stocks finished higher Thursday, pushing the Dow Jones industrial average and the Standard & Poor's 500 index to their highest levels since June of 2008. In world market news, Standard & Poor's downgraded Japan's sovereign credit rating to AA- from AA, as concerns over mounting debt rose. In U.S. economic news, the number of Americans filing for first-time unemployment benefits jumped 51,000 to 454,000 last week, according to the Labor Department. The reading was much higher than analysts expected. Meanwhile, durable goods orders for the month of December fell 2.5 percent, the Commerce Department said. Economists were expecting the reading to rise 1.5 percent. --More