Google heavily relies on links when it comes to specify the ranking of a web site. In addition to the sheer number of links and their anchor texts, the patent specification shows possible ways how Google might use historical information to further specify the value of links.
For example, Google might record the discovery date of a link and the link changes over time. Google might also record the life span of a link and the speed at which a new web site gets links.
The patent specification indicates that Google might track the following information:
The anchor text and the discovery date of links are recorded. Google might monitor the appearance and disappearance of a link over time. Google might monitor the growth rates of links as well as the link growth of independent peer documents.
Google might monitor the changes in the anchor texts over a given period of time. Google might monitor the rate at which new links to a web page appear and disappear. Google might record a distribution rating for the age of all links. Links with a long life span might get a higher rating than links with a short life span.
Links from fresh pages might be considered more important. If a stale document continues to get incoming links, it will be considered fresh. Google doesn’t expect that new web sites have a large number of links. If a new web site gets many new links, this will be tolerated if some of the links are from authorative sites.
Google indicates that it is better if link growth remains constant and slow. Google indicates that anchor texts should be varied as much as possible. Google indicates that burst link growth may be a strong indicator of search engine spam.