While the survey methodology sounds very science-y using census data and whatnot it would have been easier for researchers simply to drive through OKC and count the corners without churches. (The actual number is 21.)
OKC was ranked behind Salt Lake City and Birmingham, Ala. One of those cities has a distinct advantage as the worlds headquarters for the faith that Mitt Romney founded or something like that.
The survey tracked church attendance and membership rolls by allowing religious bodies to self-report. Thats probably a bad idea, seeing as how, professionally, church attendance and offerings are the only things ministers are permitted to lie about.