encyclo - 7:31 pm on Aug 15, 2005 (gmt 0)

From Slashdot [slashdot.org] - A Comparision of the Size of the Yahoo! and Google Indices by the National Center for Supercomputing Applications (NCSA):

[vburton.ncsa.uiuc.edu...]

(...) we found that on average Yahoo! only returns 37.4% of the results that Google does and, in many cases, returns significantly less. As our search results indicate, there are a number of cases in which Google returns dozens of results while Yahoo! only returns one or two results, or none at all.

The one caveat is that the research is based on searches with <1000 results due to the fact that neither SE shows more than 1000 ranked pages.