Ye-es… I think my point (sorry, it was extraordinarily subtle, I admit) was that perhaps the formula might be specified by place (be it county, country, city, what have you), as this one was.
(We seem to be getting a number of these similar "how do I generate results for ______" topics recently where the ______ is a place, the type of which really is not the important part, the how to part is.)
That said, I think pisum’s question of what the benefit would be of more than the top 500 results is a good one for smaller localities.