6. A computer-implemented method of assessing specificity of a search query, the method comprising: under the control of one or more computer systems configured with executable instructions, obtaining data associated with the search query, the data comprising indications of search-result items and, for each search-result item, a corresponding number of first-clicks, the search-result items being items presented to users in response to the users submitting the search query, the number of first-clicks indicating the number of times the users selected the corresponding search-result item first in time before other items; using the indications of the search-result items and the corresponding number of first-clicks to create a distribution of first-clicks across the search result items, wherein the distribution is indicative of how the first-clicks are spread across the search-result items; and determining a specificity score for the search query based at least in part on the distribution of first-clicks across the search result items, wherein the more evenly distributed the distribution of first-clicks, the lower the specificity score and the more likely the search query is submitted by users with the intention of general searching, and wherein the more skewed the distribution of first-clicks, the higher the specificity score and the more likely the search query is submitted by users with the intention of specific searching.
6. A computer-implemented method of assessing specificity of a search query, the method comprising: under the control of one or more computer systems configured with executable instructions, obtaining data associated with the search query, the data comprising indications of search-result items and, for each search-result item, a corresponding number of first-clicks, the search-result items being items presented to users in response to the users submitting the search query, the number of first-clicks indicating the number of times the users selected the corresponding search-result item first in time before other items; using the indications of the search-result items and the corresponding number of first-clicks to create a distribution of first-clicks across the search result items, wherein the distribution is indicative of how the first-clicks are spread across the search-result items; and determining a specificity score for the search query based at least in part on the distribution of first-clicks across the search result items, wherein the more evenly distributed the distribution of first-clicks, the lower the specificity score and the more likely the search query is submitted by users with the intention of general searching, and wherein the more skewed the distribution of first-clicks, the higher the specificity score and the more likely the search query is submitted by users with the intention of specific searching. 7. The computer-implemented method of claim 6 , wherein using the indications of the search-result items and the corresponding number of first-clicks to create the distribution of first-clicks across the search result items, comprises: determining a first-click probability value for each of the search-result items by dividing the number of first-clicks for the search-result item by a total number of first-clicks received across all of the search-result items.