FiveThirtyEight: Politics Done Right: Will Iowans Uphold Gay Marriage?

More intriguing stuff from good old Nate Silver … this time, estimating when a state’s population might be ready for gay marriage, or at least ready not to ban it. Given the complexity of political processes in a lot of these places – rural domination, different constitutional structures, etc. – I wouldn’t venture to say that by 2012 we’ll really have a majority of states accepting gay marriage, but the snowball is definitely picking up speed.

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.

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.

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.

It’s intriguing that education, race, and party aren’t particularly useful explanatory variables. I do get a little nervous when there’s a time variable introduced – there’s no mystical force pulling the political transformation along. And students of Roe v. Wade should recognize that these kinds of tides do turn, change course, etc.

via FiveThirtyEight: Politics Done Right: Will Iowans Uphold Gay Marriage?

One Response to “FiveThirtyEight: Politics Done Right: Will Iowans Uphold Gay Marriage?”

  1. Nate got it last night: http://www.fivethirtyeight.com/2009/04/gay-marriage-by-numbers.html