Again, religious people can be defined by the Dunning-Kruger effect.
"The data for the national IQs and percentages asserting disbelief in God for the 137 countries are given in the
Appendix A. It will be seen that in only 17% of the countries (23 out of 137) does the proportion of the population whodisbelieve in God rise above 20%.
These are virtually all the higher IQ countries. The correlations between the national IQs and religious
disbelief are given in Table 3. Row 1 gives the correlation of 0.60 for the total sample and is highly statistically significant (pb.001). To examine whether this relationship holds across the whole range of national IQs we have divided the nations into two groups of those with IQs between 64–86 and those with IQs between 87–108. Row 2 gives the data for the 69 countries with IQs between 64–86. In this group only 1.95% of the population
are non-believers. There is a range between b1% and 40%, and the correlation between the two variables is only 0.16. Row 3 gives the data for the 68 countries with IQs between 87–108. In this group 19.99% of the population disbelieve in God. There is a range between b1% and 81%, and the correlation between the two variables is only 0.54 (pb.001). Thus, most of the variation in religious disbelief is among the higher IQ nations"
http://www.midus.wisc.edu/findings/pdfs/1197.pdf
