Microsoft’s share of the U.S. search market remained level at 14.7 percent in September, the same as in August, but Yahoo’s share declined from 16.3 percent to 15.5 percent, according to comScore’s September 2011 U.S. search engine rankings..
Microsoft’s sites — primarily Bing — came in third behind Google and Yahoo. Microsoft and Yahoo have a partnership wherein Bing powers Yahoo’s searches and Yahoo sells premium ads for both.
Microsoft’s share of the search market has gone up since a year ago (when it held 11.2 percent), while Yahoo’s has gone down (Yahoo held 16.7 percent a year ago), according to comScore.
Here’s comScore’s chart: