  We carried out a retrieval effectiveness test on the three major web search
engines (i.e., Google, Microsoft and Yahoo). In addition to relevance
judgments, we classified the results according to their commercial intent and
whether or not they carried any advertising. We found that all search engines
provide a large number of results with a commercial intent. Google provides
significantly more commercial results than the other search engines do.
However, the commercial intent of a result did not influence jurors in their
relevance judgments.
