Statistics wizard Nate Silver has crunched his magical numbers and predicted when same-sex marriage bans will crumble in every state. He came up with the numbers like this:

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.

Marriage bans, however, 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.

I'm not sold -- he pegs North Carolina as not crumbling until 2019, but my experiences there tell me this state is moving on gay issues at a surprisingly fast pace. Perhaps a more useful read on this data may just be generally a scale of likelihood over the coming years, rather than taking these dates at face value.

(Via JMG)