Saturday, July 30, 2011

Fallacy of composition, W-NOMINATE version

I've been neglecting my blog lately. Much of the reason is that I've been working to understand the political science program NOMINATE, so that I can gather information about the ideological make-up of the New Hampshire legislature.

The data is posted on the W-NOMINATE page of my blog. Here's the cool graph (click to enlarge):

Keith Poole and Howard Rosenthal, the main developers of the program, claim that the program measures economic attitudes on the x-axis, and, in recent years, social attitudes on the y-axis.

At first blush this is what it appeared to be doing for New Hampshire legislators. However, after taking a closer look at the votes, I discovered that it's not doing this. At least, not very well.

The x-axis measures economic issues well, and correlates beautifully with the House Republican Alliance's scorecard ratings. (See this impressive graph, courtesy of Seth Cohn.) The y-axis, on the other hand, has issues. Apparently, because there have been so few votes on social issues this year, there is little basis for the y-values. Mostly they reflect positions on gun rights and criminal justice issues, with pro-gun and tough on crime on the bottom.

This is yet another reminder that politics at the state level does not necessarily imitate politics at the federal level.

Thanks to Rep. Seth Cohn, Scott Pauls at Dartmouth, and professor Jason Sorens for criticism and help. Peer review fixed my mistake.

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