Predicting The Future Of Marriage Equality in the U.S.

A blogger by the name of Map Scroll has taken über-geek Nate Silver's soon-to-be famous post presenting a model predicting when a public vote on marriage equality will be favorable for the forces of equality and put it in the form of an easy-to-digest map of the United States.

Silver came to prominence with his shockingly accurate predictions in the 2008 election season and continues to provide fascinating examples of applying mathematics to what the general public generally believes are non-mathematical topics, such as whether anti-gay marriage ballot measures will pass or fail in the future:

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.

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.

This would tend to support the position of Love Honor Cherish and other grassroots marriage equality organizations about going back to Califonia voters in 2010 or waiting until 2012 to repeal Proposition 8. Most of the "grasstops" organizations like the L.A. Gay and Lesbian Center and (tacitly) Equality California and the National Center for Lesbian Rights seemed to endorse the later date at the recently Town Hall on Marriage Equality MadProfessah was invited to appear at last week.

My position is that we should go back to the ballot (in November 2010) and if we lose there be prepared to go back in November 2012 also.

Silver is good, but he isn't perfect. His attempt at predicting the Oscar results this year was pretty laughable.