This is a hard issue to analyze when most countries don't gather data on IQ that are comparable at all from country to country, and when there is considerable disagreement about what we mean by "religion."
It is becoming a firmly established research finding that rationality is weakly correlated with IQ,
with many high-IQ individuals exhibiting extremely poor rationality, so even if we knew differing IQ distributions for countries around the world reliably, which we do not, we would have no idea from those statistics which countries have a populace that tends to act rationally.
http://www.stat.columbia.edu/~cook/movabletype/archives/2010...
http://wicherts.socsci.uva.nl/wichertsPAIDrejoinder.pdf
http://wicherts.socsci.uva.nl/wichertsRavenAfr2010rej.pdf
http://wicherts.socsci.uva.nl/APA02.pdf
This is a hard issue to analyze when most countries don't gather data on IQ that are comparable at all from country to country, and when there is considerable disagreement about what we mean by "religion."
It is becoming a firmly established research finding that rationality is weakly correlated with IQ,
http://www.project-syndicate.org/commentary/stanovich1/Engli...
http://www.oup.com/us/catalog/general/subject/Psychology/Cog...
with many high-IQ individuals exhibiting extremely poor rationality, so even if we knew differing IQ distributions for countries around the world reliably, which we do not, we would have no idea from those statistics which countries have a populace that tends to act rationally.