ANOTHER GAIN: The Dow Jones industrial average eked out a small gain and advanced for an eighth straight day. That's the longest streak of gains for the index since February 2011.

DRUGS TEST: Merck pulled the Dow higher, advancing 3.2 percent to $45.04 after the drugmaker said a data safety monitoring board recommended that a study of its cholesterol drug Vytorin should continue.

PULLBACK COMING?: Many analysts predict that, after a big gain for stocks early in the year, there will be a pullback at some point. The Dow is up 10.3 percent in 2013 and the Standard & Poor's 500 index is 8.9 percent higher.