It’s always been an uphill battle for Bing, trying to gain search market share, but it doesn’t help when search giant Google’s market share grows too. And for as much fuss that has been made in the media about Google’s privacy policy and the addition of “Search Plus Your World” to Google results, Google still managed to gain market share in the U.S. last month, according to the latest data from comScore.

Google Sites led the “explicit core search market” with 66.4% of queries, according to the firm. That’s up 0.2 percentage points from January.

Microsoft sites (including Bing, obviously) had 15.3%, up 1 percentage point. Yahoo lost .3 percentage points, falling to 13.8%. Ask maintained 3% month to month, while AOL dropped 0.1 percentage points to 1.5%

comScore reports:

17.6 billion explicit core searches were conducted in February, with Google Sites ranking first with 11.7 billion. Microsoft Sites ranked second with 2.7 billion searches, followed by Yahoo! Sites with 2.4 billion, Ask Network with 535 million (up 2 percent) and AOL, Inc. with 266 million.

It’s interesting that Yahoo is on the decline as Microsoft continues to increase, considering Bing powers Yahoo these days, and adCenter powers Yahoo Search Marketing. It will be something to keep an eye on as new Yahoo CEO Scott Thompson is with the company for a longer amount of time. Yahoo is much more than a search company of course, and we have to wonder how big of a priority search will be under the new leadership.

Yahoo turned 17 last week.