A lot of people like to think search engines aren’t that different. They index the same internet, and they return mostly the same results, right? Not at all. A new study shows once again that search engines index mostly unique pages and rank common ones completely differently. This should carry a heavy message for optimizers, and a smaller one for searchers.
Pennsylvania State University and Dogpile.com studied the overlap in results that the four major search engines (Google, Yahoo!, MSN Search, and Ask Jeeves) provided.
The study used 485,460 unique searches in July 2005. The researchers only looked at the total results and found this information:
84.9% results were unique to one search engine.
11.4% results were shared by any two search engines.
02.6% results were shared by three search engines.
01.1% results were shared by the top four search engines.
It’s actually amazing how little agreement there is between search engines. It has a lot of implications. Primarily, people should be concerned because searchers and marketers can miss out on huge market segments. By focusing on only one search engine, you can miss a lot.
Google misses 70.8% of first page results on other engines.
Yahoo! misses 69.4% of first page results on other engines.
MSN Search misses 72.0% of first page results on other engines.
Ask Jeeves misses 67.9% of first page results on other engines.
This shows how completely different search engines are. Each has its own personality when it comes to evaluating and delivering the web’s most important content. Relevancy of results is also questioned with a study by comScore Media Metrix, which found that 31 to 56% of searches on these top search engines elicit a first page click. If half (or more) of searchers are not clicking on a first page result, did the search engine deliver irrelevant or useless results?
The study also found that, “Only 4.7% of Yahoo! and Google sponsored links overlap for a given query.” This means that companies paying to advertise are only considering one search engine or another. As we will take a look at on the following page, this kind of marketing is short sighted and misses huge numbers of potential customers.
For the source of all this information, and to read more interesting details, drop by Dogpile’s 30 page PDF at http://comparesearchengines.dogpile.com/OverlapAnalysis. It’s an interesting read, though mostly written to show that searchers may find Dogpile useful.
Search Optimization 
