Bing achieved the highest success rate in December 2010: 81 percent. Google meanwhile achieved a success rate of 65 percent, up 1 percent over the previous month, according to Experian Hitwise.

A successful search is defined as one where the user ends up visiting a website, as opposed to clicking back or searching again with a new query. Both Google and Bing offer quick answers directly in their search results, which sometimes makes it unnecessary to click a link, but we doubt those searches account for anywhere between 19 to 35 percent.

The share of unsuccessful searches shows how much both search engines can still improve their result pages to ensure that users are finding the information they are seeking. Microsoft has said before that one of the reasons it insists on competing with Google is because search is not solved.

Google accounted for 69.67 percent of all US searches conducted in the four weeks ending January 1, 2011. Bing-powered search received 25.77 percent of searches for the month. Breaking that last number down, Yahoo accounted for 15.17 percent while Bing had 10.60 percent. The remaining 70 search engines tracked by Hitwise accounted for 4.57 percent of US searches.