comScore released its search engine rankings for the United States for May 2012 today and, as far as month-to-month changes go, very little has in fact changed among the market shares claimed by the top search sites. For once, that’s good news for Yahoo.

Google continues to leave a very deep imprint on the cushions of the search engine couch, remaining the number one search brand for the umpteenth month in a row with 66.7% of the market share, which is up .02% from April’s report. Microsoft sites, which include the company’s search engine, Bing, retained the second-highest rank but had a fairly flat month as its market share didn’t budge even a fraction of a percent. Yahoo continued its slow slip in the market but not nearly as bad as previous months while the Ask Network and AOL rounded out the top five.

Microsoft’s sites gained a little bit among explicit core search queries and although the amount was less than one hundred, it was still a 2% increase from last month. Google added over 600 explicit core search queries in May, an increase of 3%. Yahoo, Ask, and AOL, respectively, again rounded out the top five search brands.

In both terms of both market share and explicit core search queries, at least Yahoo was able to stop the skid it’s experienced for much of 2012. From March to April, the company lost 2.4% of its market share to Bing and Google. It’s the middle of the year now and Yahoo has certainly had a tumultuous 2012 thus far, so maybe the second half of the year will see sunnier skies for Yahoo.

comScore notes that last month, 68.9 percent of searches carried organic search results from Google (up 0.2 percentage points versus April), while 25.6 percent of searches were powered by Bing.