It appears so. There is a growing body of evidence (here and here and here) that the degree of religosity is directly and positively correlated to adverse social conditions. What this means is that the influence of religion can best be reduced by eliminating those adverse social conditions that promotes it.
So how do we know if economic inequality is an important and significant factor?
In a new paper Economic Inequality, Relative Power, and Religiosity, the authors have collected data from 76 countries using 12 different measures for strength of faith where we see this very strong correlation:
Across the bottom is the income inequality per country compared to the left column as a frequency of occurrence of whatever the stated question asks. As we can see, the lower the inequality, the lower the frequency, the higher the inequality, the higher the frequency. This is statistically significant and helps to explain that even in developed countries, the impetus for religiosity is based on social conditions that promote economic inequality and not on the truth value of the religious claims themselves.
So is religiosity growing or declining in the United States?
Interesting, eh? This is good evidence that the assumption made by accommodationists – that we need to be less, and not more, critical of religious interference in order to promote science – seems to be misguided. Equitable economic factors seems to be primary.
For a more in-depth look at this study and some of the important questions it raises, check out Jerry Coyne’s assessment and many excellent comments at Why Evolution is True.