what was the methodology to determine it
As far as I can determine, it's derived from a poll taken by the Public Religion Research Institute, which claims to be nonpartisan. My instinct tells me their a leftist outfit but, that said, as one who frequently traveled, it does seem right. It's no surprise that Portland, OR leads the list of this rogue's gallery of places that are anti-God. It has a lot of hippie types and good number of the thug element (I almost got mugged there several years ago). Plus Oregon allows "doctor" assisted suicide, a direct repudiation of God's Laws.
I agree
This list is not very accurate
nortex....this is a bull hit job article
See church attendance and professed Christians per city here
http://leadnet.org/most_and_least_unchurched_cities/