Percent of searches done in US, June 2008.
(source Nielsen [1])

Search Company

percent of searches

cumulative percent

Google

59.30%

59.30%

Yahoo!

16.90%

76.20%

MSN/LiveSearch

13.30%

89.50%

AOL

4.10%

93.60%

Ask.com

2.10%

95.70%

[1]     Bausch, Suzy and McGiboney, Michelle. 2008. Nielsen Online Announces May U.S. Search Share Rankings Nielsen/NetRatings, Inc. June 19, 2008 DOI=http://www.nielsen-netratings.com/pr/pr_080619V.pdf