Why gay marriage will (eventually) pass in all US states (even Mississippi)

The decision of California's Supreme Court to reject the challenge to the ban on gay marriage – Proposition 8 – voted on by the people in November 2008, seems to have excited much 'woe is us' comment (as well as rallies in 104 American cities and towns last night).

Alistair Campbell even blogged that:

It left millions across the state and across America in despair wondering when they will get the opportunity to be treated equally in the eyes of the law and of society.

Yesterday’s decision cancelled out much of what San Francisco gay rights campaigner Harvey Milk, the subject of a brilliant recent film – and many others – worked for. It may be years until gay Californians again have the rights already enjoyed by the people of Iowa, Connecticut, Maine, Massachusetts and Vermont.

Actually, I suspect Milk would have had more of a sense of proportion and definitely more of a sense of history.

Prop 8 - gay marriage remember, not civil partnerships (that weird 'seperate-but-equal' status which gave Tony Blair a nice liberal shiver) - came within a couple of points of being defeated.

Already activists have vowed to try again ASAP. And they'll get what they want - something Milk probably didn't even dream of - real equality.

It's inevitable because the culture is only going in one direction - pro-equality.

The stats whiz Nate Silver, THE 'go-to' guy when it comes to reading poll results (and other predictive factors), who best predicted the 2008 Presidential race (and who I referenced a lot in my posts about that) says so.

Following the passage of gay marriage in Iowa he built a predictive model whose outcome is that gay marriage will come in every US state by 2024, with half getting there by 2012. He discovered that you can build it on only 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.

Its accuracy is such that:

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.

Because of changes in US society:

Marriage bans are losing ground at a rate of slightly less than 2 points per year.

Below are the dates when the model predicts that each of the 50 states would vote against a marriage ban. Asterisks indicate states which had previously passed amendments to ban gay marriage.

2009 (now)
Vermont
New Hampshire
Massachusetts
Maine
Rhode Island
Connecticut
Nevada*
Washington
Alaska*
New York
Oregon*

2010
California*
Hawaii
Montana*
New Jersey
Colorado*

2011
Wyoming
Delaware
Idaho*
Arizona*

2012
Wisconsin*
Pennsylvania
Maryland
Illinois

2013
Michigan*
Minnesota
Iowa
Ohio*
Utah*
Florida*

2014
New Mexico
North Dakota*
Nebraska*
South Dakota*

2015
Indiana
Virginia*
West Virginia
Kansas*

2016
Missouri*

2018
Texas*

2019
North Carolina
Louisiana*
Georgia*

2020
Kentucky*

2021
South Carolina*
Oklahoma*

2022
Tennessee*
Arkansas*

2023
Alabama*

2024
Mississippi*

So don't worry, be happy! :]

Postscript: The ruling, as with the original vote, has stirred up a massive grass-roots movement for LGBT civil rights in the United States. Protests happened in 104 American cities the night of the decision and are notable for the engagement of a new generation many thought too interested in partying.

Last night protesters came out in force when Obama came to LA for a Democratic Party fundraiser - led by Lt. Dan Choi, the West Point graduate and Arabic linguist fired for being gay. They see Obama putting off repealing 'don't ask, don't tell'.

One of the things which Obama repeatedly said during the campaign was that in order for him to help make change happen he needed to see a grass-roots movement piling on the pressure.

Anybody who’s been at an LGBT event with me can testify that my message is very explicit -- I don’t think that the gay and lesbian community, the LGBT community, should take its cues from me or some political leader in terms of what they think is right for them. It’s not my place to tell the LGBT community, "Wait your turn." I’m very mindful of Dr. King’s “Letter From Birmingham Jail,” where he says to the white clergy, "Don’t tell me to wait for my freedom."

Well, it's happening.

• Another Prop 8 postscript