Actually, one of the first maps presented in the book is broken down not by "Protestant Europe", "Catholic Europe", etc, but by income, low/middle/high, with the economic zones taken from the World Bank's World Development Indicators, 2002. I didn't see this map on the website. Frankly I paid more attention to the book which goes into greater detail on the methodology and theoretical spadework the authors rely on.

"It Can't Be Just About Us"
--Frank Schnittger, ETian Extraordinaire