Tuesday, June 16, 2009

we developed statistical tools for estimating public opinion among subsets of the population

TO BE NOTED: From Statistical Modeling, Causal Inference, and Social Science:

Who wants school vouchers? Rich whites and poor nonwhites

As part of our Red State, Blue State research, we developed statistical tools for estimating public opinion among subsets of the population. Recently Yu-Sung Su, Yair Ghitza, and I applied these methods to see where school vouchers are more or less popular.

We started with the 2000 National Annenberg Election Survey, which had responses from about 50,000 randomly-sampled Americans to the question: "Give tax credits or vouchers to help parents send their children to private schools--should the federal government do this or not?" 45% of those who expressed an opinion on this question said yes, but the percentage varied a lot by state, income level, and religious/ethnic group; These maps show our estimates:


(Click on image to see larger version.)

Vouchers are most popular among high-income white Catholics and Evangelicals and low-income Hispanics. In general, among white groups, the higher the income, the more popular are school vouchers. But among nonwhites, it goes the other way, with vouchers being popular in the lower income categories but then becoming less popular among the middle class.

You can also see that support for vouchers roughly matches Republican voting, but not completely. Vouchers are popular in the heavily Catholic Northeast and California, less so in many of the mostly Protestant states in the Southeast. We also see a regional pattern among African Americans, where vouchers are most popular outside the South.

We checked our results by fitting the same model to the Annenberg survey from 2004, and, much to our relief, we found similar patterns:

In 2004, 52% of respondents supported vouchers, but it's difficult to make a direct comparison to the 2000 survey because the question was worded differently: instead of yes/no, it was, "The federal government giving tax credits or vouchers to help parents send their children to private schools--do you favor or oppose the federal government doing this?" with five possible responses. We counted the two positive responses as Yes, the two negative responses as No, and discarded the 30% or responses in the middle category. The total Yes/(Yes+No) was 52%. Anyway, here's what we found when breaking up by state, income, and religion/ethnicity. Again, colors are relative to the national average:


(Click on image to see larger version.)

In checking these results, we made a series of plots showing raw data and fitted models. Here's one of the sets of graphs, just to give a sense of what we did:


(Click on image to see larger version.)

Finally, all estimates were adjusted to the estimated population of voters, using our voter turnout analysis from the 2008 Current Population Survey post-election supplement and American Community Survey data. We'll write this up in detail at some point. It would be best for us to redo 2000 and 2004 using the voter turnout estimates for those years, but we haven't gotten around to putting those numbers together yet. I don't think it will make much of a difference.

Also, I don't think the labels on the income categories are exactly right for 2000 and 2004. I realize I was taking income categories from a different poll. We need to look up the categories from the Annenberg surveys."

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