The Human Development Index (HDI) is a measure of the quality of life in a country.
Gallup poll compiled a ranking in 2009 of the most to least religious countries.
When I looked at the two, I noticed a trend. Some of the worst places on the planet, as measured by HDI were also some of the most religious places.
The US seems to be the obvious exception to the rule, but if you look closely at the US, you see the trend reflected there as well. The most religious states are also the poorest states.