Statistical religious bigotry [updated]

Nate Silver crunches some numbers:

Marriage bans [are] losing ground at a rate of slightly less than 2 points per year. So, for example, we'd project that a state in which a marriage ban passed with 60 percent of the vote last year would only have 58 percent of its voters approve the ban this year.

So not only does the arc of the universe bend towards justice, but we can measure the degree of that bend... here's the methodology:

I looked at the 30 instances in which a state has attempted to pass a constitutional ban on gay marriage by voter initiative. The list includes Arizona twice, which voted on different versions of such an amendment in 2006 and 2008, and excludes Hawaii, which voted to permit the legislature to ban gay marriage but did not actually alter the state's constitution. I then built a regression model that looked at a series of political and demographic variables in each of these states and attempted to predict the percentage of the vote that the marriage ban would receive.

It turns out that you can build a very effective model by including just three variables:

1. The year in which the amendment was voted upon;
2. The percentage of adults in 2008 Gallup tracking surveys who said that religion was an important part of their daily lives;
3. The percentage of white evangelicals in the state.

These variables collectively account for about three-quarters of the variance in the performance of marriage bans in different states. The model predicts, for example, that a marriage ban in California in 2008 would have passed with 52.1 percent of the vote, almost exactly the fraction actually received by Proposition 8.

Unsurprisingly, there is a very strong correspondence between the religiosity of a state and its propensity to ban gay marriage, with a particular "bonus" effect depending on the number of white evangelicals in the state.

[...] All of the other variables that I looked at -- race, education levels, party registration, etc. -- either did not appear to matter at all, or became redundant once we accounted for religiosity. Nor does it appear to make a significant difference whether the ban affected marriage only, or both marriage and civil unions.

Inside the Christianist mind

I recently spoke with someone who is very unhappy with the Iowa ruling. He is a white evangelical whose religion is certainly a very important part of his daily life. So anecdotally I knew this correspondence was true, but it's good to know it holds up statistically.

Update: In an effort to help him out, I sent a link to a post by hilzoy which I think does a great job of explaining how to be a Christian in a secular world. His response? ...

You have missed it again! And you will continue to miss it. This policy will set up a nazi like behavior towards Christians and other religious groups. We never killed gays or imprisoned them for private behavior but this will now move step by step to deny religious freedom. It will move to jail and finally planned extermination. One right of both Christians and probably other groups as well will be taken away. It will start that we can't discriminate against gays and then it will move for other reasons that seem logical to the secular mind. It isn't a gay thing but rather it is a light versus darkness thing. It started in earnest in the Thirties and it has continued. Abortion was a baby step and this will be another in its plan. We will be discriminated against continually like the last 40 years and it will get worse. This is a collision course towards the policies of the Roman Empire and the Communist era of Stalin. But behind it all is not a human face or agenda. You can't see it because you have lost yourself in this world's agenda and are now blind.

Sometimes the fundamentalist paranoia of white evangelicals really shines bright, no?