David noticed this article by Dan Mitchell reporting the well-known fact that people in richer countries tend to be less religious. What about states in the U.S.? We (that is, David Park, Joe Bafumi, Boris Shor, and I) look at it two ways.
First, here’s a scatterplot of the 50 states, plotting average religious attendance vs. average income. (Religious attendance is on a -2 to 2 scale, from “never” to “more than once a week,” and average income was originally in dollars but has been rescaled to be centered at zero.):
States that voted for Bush in 2004 are in red and the Kerry-supporting states are blue. You can see that people in richer states tend to be less religious, although the relation is far from a straight line. There is also some regional variation (more religious attendance in the south, less in the northeast and west).
Second, here’s a plot showing the correlation of religious attendance and individual income within each state. We get a separate correlation for each state, and so we can plot these. Here we plot the correlations vs. state income, using the same color scheme:
Again, there’s quite a bit of variation from state to state, but overall we see a positive correlation between income and religiosity in poor states and a negative correlation in rich states: To put it another way, in Mississippi, the richer people attend church more. In Connecticut, the richer people attend church less.
P.S. Typos fixed (thanks to commenters Derek and Sandapanda).
P.P.S. Colors of Iowa and New Mexico fixed (thanks to commenter David).