Below is an interactive chart containing the major search engines (Google, Yahoo, Microsoft sites(MSN), Ask.com, AOL) percentage usage (for the period May to October 2009). (from Comscore)
Yahoo! has decreased to 18 % from 20.1 % in the last 6 months.
Bing has gained 1.9 % in the last 6 months. (from 8% to 9.9 %).
In October, Google and Bing have gained 0.5% each at the cost of Yahoo! ‘s search share.