Saturday, March 15, 2014

POLL ANALYSIS: Support For Marriage Equality Is Accelerating!

Andrew Flores of the Williams Institute has a piece of the Monkey cage blog that analyzes the latest polls on marriage equality and makes a compelling argument that support for marriage equality is increasing at an increasing rate. (For you Calculus fans, we say that the graph of public support for marriage equality is "concave up"). The key point he makes is that since the Supreme Court issued its two marriage equality decisions (United States v. Windsor striking down the Defense of Marriage Act and Hollingsworth v. Perry effectively nullifying California's Proposition 8) in June 2013 (a date I like to call Gaytterdämmerung) popular support for marriage equality has ratcheted upwards at an accelerating pace.

The graphs below compare  the polling trends using a linear model or a polynomial model. It turns out that a polynomial model fits the polling data pre-Windsor and post-Windsor better than the linear model does for either time period..
This is a direct refutation of the idea that Kevin Drum posited recently that popular opinion on marriage equality has evolved about as rapidly as it did on interracial marriage. It also challenges an idea that Nate Silver promoted awhile back that the shift was due to opponents dying off and being replaced by a younger cohort which is overwhelmingly in support of marriage equality, leading him to predict an increase in support of roughly .5 percentage points per year in national polls.

Having a good estimate of the rate of increase in support for marriage equality is important, because as Flores says:
This has important implications for where public opinion is headed. If the stable linear trend were the right one, then by 2016 just over 56 percent of the public would be expected to support same-sex marriage. However, the accelerated trend predicts that support for same-sex marriage will be about 5 points higher by 2016. It is appropriate to infer that opinions are trending positively and changing exponentially as time goes on.
Regardless how you slice it, this is "good for the gays"!

(However, as a mathematician I truly wish that he hadn't used the word "exponentially" in that last sentence. There's a huge difference between polynomial growth and exponential growth. I think he meant the former when he said the latter. Regardless, it is still a good piece that I encourage you to read in full!)

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