Google lead at 67.3%, with Microsoft sites at 18.2%, and Yahoo sites at 10.8%.
 

Google Sites led the U.S. explicit core search market in December with 67.3 percent market share (up 0.6 percentage points), followed by Microsoft Sites with 18.2 percent (up 0.1 percentage points) and Yahoo Sites with 10.8 percent. Ask Network accounted for 2.5 percent of explicit core searches, followed by AOL, Inc. with 1.3 percent.comScore: December 2013

18.3 billion explicit core searches were conducted in December, with Google Sites ranking first with 12.3 billion (up 2 percent). Microsoft Sites ranked second with 3.3 billion searches (up 1 percent), followed by Yahoo Sites with 2 billion, Ask Network with 452 million and AOL, Inc. with 234 million.