By comparing results between leading search engines, we identify patterns in their algorithmic search listings. We find that each search engine favors its own services in that each search engine links to its own services more often than other search engines do so. But some search engines promote their own services significantly more than others. We examine patterns in these differences, and we flag keywords where the problem is particularly widespread. Even excluding "rich results" (whereby search engines feature their own images, videos, maps, etc.), we find that Google's algorithmic search results link to Google's own services more than three times as often as other search engines link to Google's services. For selected keywords, biased results advance search engines' interests at users' expense: We demonstrate that lower-ranked listings for other sites sometimes manage to obtain more clicks than Google and Yahoo's own-site listings, even when Google and Yahoo put their own links first.
