9. The method of claim 7 , wherein the interpolation function is a non-linear interpolation function.
7. The method of claim 5 wherein providing the estimated relevance value for each search result without an actual relevance value supplied by the search engine that provided the search results comprises: determining an interpolation function, to represent relevance as a function of rank, for the actual relevance values and the ranks of the at least two others of the search results for the search engine; and evaluating the interpolation function at the rank of the particular search result to estimate the relevance value.