Where are the seculars?

Over at Island of Doubt James Hrynyshyn says:

As far as I can tell, North Carolina's no different from the rest of America when it comes to religion. About a tenth of the population is free of religious conviction....

Well, I was pretty sure that there is a statistically significant difference between most Southern states and the rest of the country in regards to these things, so I decided to check out the data in detail. The US Religious Landscape Survey allows me to see what proportion of each state's population are atheists; that is, they don't believe in God. Unfortunately the margin of errors are relatively big because of small sample sizes from the unbelievers for most states, so I wanted an outside "check," and luckily the American Religious Identification Survey has state-by-state breakdowns as well. But, their breakdowns are for those with "No Religion," a category where the rule of thumb is only 1/3-1/2 are atheists. Out of curiosity I plotted the number of atheists on the X axis vs. the nonreligious on the Y axis.

The geographic patterns are interesting. Note that the West has many nonreligious, or those who are not affiliated. In contrast, parts of the Northeast have a great number of atheists, but lack of affiliation is relatively rare in comparison to someplace like Washington or Wyoming. The American South is a relatively distinctive cluster as well, with low levels of atheism and high rates of affiliation. The Midwest is a bit more diverse, but you can also see a discernible cluster there, with similar rates of affiliation as much of the Northeast but lower rates of atheism. The raw data is below the fold....