Nielsen//NetRatings found that in June and July of this year the major search engines enjoyed high user retention but also high audience overlap, suggesting that audiences are actively using two and three engines. Search engines saw the highest user retention of the three categories that Nielsen compared and examined (search, travel, jobs).
According to the release:
Among the categories, search providers had the highest visitor retention rates, with an average of 71 percent of June visitors at home returning in July among the three leading search players. Google Search led with a retention rate of 79 percent, followed by Yahoo! Search at 69 percent and MSN/Windows Live Search with 65 percent (see Table 1). Visitor retention rates were slightly higher among the work audience, with an average of 76 percent among the three leading search providers.
Notably though, a substantial portion of visitors went to more than one of these three search sites in July. MSN/Windows Live Search had the highest audience overlap, with 84 percent of its unique visitors also going to Google Search, Yahoo! Search, or both. Yahoo! Search had a 78 percent audience overlap with Google and/or MSN, while Google Search had a 63 percent audience overlap with one or both of its two primary competitors.
Google shows the lowest degree of overlap, indicating that it’s the primary search engine for the highest number of users. However, the degree of overlap and active use of Yahoo and Microsoft by so many Google users suggests that some amount of usage could shift to Yahoo or Microsoft as the primary engine if there were sufficient justification for doing so (i.e., some dramatic feature innovation or visibly improved relevance vs. the others).