Though Google remains firmly on top of the search engine market, it's shed market share to Microsoft over the past year, according to data released last week by research firm Compete.

Looking at the overall search engine market from May 2010 to May 2011, Compete found that Google has lost close to 16 percent of its share, dropping to 63.6 percent from 73.9 percent. At the same time, Microsoft grew its share by 75 percent, jumping to 17 percent from 9.7 percent.

The other three search engines tracked--Yahoo, Ask, and AOL--grew only slighty over the past year, showing that most of Bing's gain has been at the expense of Google.

The number of search queries on each site also showed a gain for Microsoft, according to Compete. Google's query volume fell to 9.5 million in May, compared with 10.8 million a year ago, a 12.4 percent loss. The number of queries for Microsoft rose to 2.5 million last month from 1.4 million last May, an increase of 78 percent.

Looking at the number of actual Web site visitors, Google drew 138 million people to its site in May, compared with 162 million in May 2010, a drop of almost 15 percent. In contrast, Microsoft saw its visitors climb to 93 million last month, compared with 61 million in May of last year, a jump of 53 percent.