31. A method performed by one or more server devices, the method comprising: determining, by one or more processors associated with the one or more server devices, a measure of how a content of a document changes over time, as a function of: an update frequency based on a number of updates of the content of the document over time, and an update amount based on: how much visible content of the document, out of a total amount of visible content of the document, has changed over time, and at least one of: a quantity of new pages added to the document over time, or a ratio of a quantity of new pages associated with the document over time versus a total quantity of pages associated with the document; generating, by one or more processors associated with the one or more server devices, a score for the document based on the measure of how the content of the document changes over time; and ranking, by one or more processors associated with the one or more server devices, the document with regard to at least one other document based on the score.
32. The method of claim 31 , where the update frequency is based on an average time between updates of the content of the document.