Google Search 191
unemployment levels and provide the information faster than traditional reporting methods and government surveys.
Search engine
PageRank
Google's rise to success was in large part due to a patented algorithm
called PageRank that helps rank web pages that match a given search
string.[11] When Google was a Stanford research project, it was
nicknamed BackRub because the technology checks backlinks to determine
a site's importance. Previous keyword-based methods of ranking search
results, used by many search engines that were once more popular than
Google, would rank pages by how often the search terms occurred in the
page, or how strongly associated the search terms were within each
resulting page. The PageRank algorithm instead analyzes human-generated
links assuming that web pages linked from many important pages are
themselves likely to be important. The algorithm computes a recursive
score for pages, based on the weighted sum of the PageRanks of the
pages linking to them. PageRank is thought to correlate well with human
concepts of importance. In addition to PageRank, Google, over the
years, has added many other secret criteria for determining the ranking
of pages on result lists, reported to be over 200 different
indicators.[12] The specifics of which are kept secret to keep spammers
at bay and help Google maintain an edge over its competitors globally.Search results
The exact percentage of the total of web pages that Google indexes are not known, as it is very difficult to accurately
calculate. Google not only indexes and caches web pages, but also takes "snapshots" of other file types, which
include PDF, Word documents, Excel spreadsheets, Flash SWF, plain text files, and so on.[13]Except in the case of
text and SWF files, the cached version is a conversion to (X)HTML, allowing those without the corresponding
viewer application to read the file. Users can customize the search engine, by setting a default language, using the
"SafeSearch" filtering technology and set the number of results shown on each page. Google has been criticized for
placing long-term cookies on users' machines to store these preferences, a tactic which also enables them to track a
user's search terms and retain the data for more than a year. For any query, up to the first 1000 results can be shown
with a maximum of 100 displayed per page. The ability to specify the number of results is available only if "Instant
Search" is not enabled. If "Instant Search" is enabled, only 10 results are displayed, regardless of this setting.