9. The method of claim 8 , wherein applying the backoff model comprises applying a plurality of backoff models that model successively larger user classes.
8. A computer implemented method of retrieving information, comprising: receiving a user query from a user along with user information indicative of a location from which the user submitted the query; receiving search results based on the user query; utilizing a computer processor that is a component of the computer to apply to the search results a geographic class model that models a first set of geographic classes by grouping a plurality of preexisting queries into multiple geographic classes based on which of a first category of geographic units is assigned to each of the preexisting queries, and wherein applying the geographic class model to the search results further comprises applying the geographic class model so as to compare the user information and the user query to the first set of geographic classes so as to determine which of the search results are most likely desired by the user; applying to the search results a backoff model that models a second set of geographic classes by grouping the plurality of preexisting queries into multiple geographic classes based on which of a second category of geographic units is assigned to each of the plurality of preexisting queries, and wherein applying the backoff model to the search results further comprises applying the backoff model so as to compare the user information to the second set of geographic classes so as to determine which of the search results are most likely desired by the user, and wherein the first category of geographic units is smaller than the second category of geographic units in that a unit of the first geographic category encompasses less geographic space than a unit of the second geographic category; ranking the search results based on said applications of the geographic class model and the backoff model; and returning the search results to the user.