On August 8th, 2005, Tim Mayer of Yahoo ! posted on the Yahoo ! Search Blog that the Yahoo ! index now provides access to over 20 billion items, which include 19.2 billion web documents, 1.6 billion images, and over 50 million audio and video files. Two days later, on his blog, University of California at Berkeley Visiting Professor John Battelle reported that Google refuted this claim saying their scientists are not seeing the increase claimed in the Yahoo ! index. In order to test Yahoo !’s claims, Matthew Cheney and Mike Perry conducted a brief study of the indices of the two search engines and then conducted a followup study to deal with the presence of "wordlists" and "dictionaries" in the results.

Read the entire research report ... (NCSA)