1. A computer-implemented method for updating a search index to identify documents with spiking interest, the method comprising: periodically receiving, at a first computing device having a processor and a memory, a history file from each of a plurality of second computing devices, the history file including a uniform resource identifier (URI) that has been accessed via a respective one of the plurality of second computing devices and metadata indicating a time of day when the URIs were accessed, wherein the plurality of second computing devices form a group of second computing devices; determining a number of instances of the URI in the history files for the group of second computing devices, wherein the number of instances occurs in a predetermined time period between a given start and stop time; calculating, automatically without user interaction, an average number of instances of the URI in the history files for the group of second computing devices, wherein the average number of instances occurs in the predetermined time period over a predetermined number of previous days, and wherein the predetermined time period is between the given start and stop time each day; determining that the number of instances of the URI in the history file is at least a predetermined amount greater than the average number of instances of the URI in the history files by, automatically without user interaction, comparing the number of instances of the URI for the group of second computing devices to the average number of instances of the URI over the predetermined number of days for said group of second computing devices; identifying the URI as a spiking URI when the number of instances of the URI is at least a predetermined amount greater than the average number of instances of the URI occurring over the predetermined number of days; and updating a search index to indicate the spiking URI, the search index being useable by a search engine to identify search results for a search query.
4. The method of claim 1 , wherein each of the second computing devices includes a browser application that generates the history file and communicates the history file to the first computing device.