Nielsen released their search engine usage statistics for December 2006 and I thought I’d share the results.  Nielsen//Net Ratings gathers data from over one million Internet users in the United States with Nielsen tracking software installed on their home and work computers that records every site visited. Measuring three unique metrics, these statistics provide a view of actual search engine usage.

According to Nielson//NetRatings, an estimated 3 billion searches were performed at Google Search in the U.S. during the month of December 2006, representing nearly 51% of all search queries performed in the U.S. during that month.  This is up from 49.5% of searches for the month of November.

Rounding out the Top 10 are:
Yahoo: 23.6%
MSN/Windows Live Search: 8.4%
AOL: 6.1%,
MyWay: 2.4%, 2.1%
Earthlink Search: 0.5% 0.5%
Comcast Search: 0.5%
NexTag Search: 0.4%

Keep in mind that this statistic specifies the number of queries conducted– NOT the number of unique visitors to the site.  However, Google now ranks #2 for unique audience, surpassing Yahoo in the list of Top 10 Parent Companies in percent reach with nearly 95 million unique visitors on the home panel and 47 million on the work panel using the Google suite of sites and tools.  Yahoo fell to just under 94 million visitors (home panel) between November and December.  Still dominating the internet in terms of audience is Microsoft, with over 103.5 million unique home visitors and 51 million office workers (a whopping 88% reach in the workplace) in December 2006.  A notable addition to the Top 10 on the work panel is Wikipedia, with a 33.5% reach.

You can find more monthly data at Nielson//NetRatings.