07/11/2008 05:14 pm ET Updated May 25, 2011

Moore: USA Today's Cluster Analysis of Voters - How Useful?

Today's Guest Pollster article comes from David W. Moore, a senior fellow with the Carsey Institute at the University of New Hampshire. He is a former vice president and senior editor with the Gallup Poll, where he worked for 13 years, and is the founder and former director of the UNH Survey Center. He manages the blogsite, Skeptical

On Thursday, July 10, USA Today published an analysis of voter intentions that produced "six types of voters" who the paper claims "will decide the presidential election." The types included: true believers (30 percent of the electorate), up for grabs (18 percent), decided but dissatisfied (16 percent), fired up and favorable (14 percent), firmly decided (12 percent), and skeptical and downbeat (12 percent).* As Mark Blumenthal indicated, this is a fascinating analysis, but how useful is it for understanding the election?

The six types of voters were produced using cluster analysis. This statistical technique is similar to factor analysis, except that it classifies respondents into distinctive groups, while factor analysis classifies various opinions into distinctive groups. Without going into the details of how the technique works, I think it's sufficient to note that the analyst has a great deal of control over the types of groups produced by cluster analysis. The analyst chooses the variables that are used to classify respondents, and also determines how many groups the cluster analysis produces. The fact that the analyst chose six clusters, instead of any other number between two and ten, was purely a subjective decision.

What is most surprising about the analysis is that it is issue free. The stereotypical complaint by political observers about the news media is that reporters focus on the horserace almost to the exclusion of any real substantive issues. This USA Today analysis fits that criticism to a T. I believe there is a widespread consensus among political observers these days that the war in Iraq (and national security more generally), the economy, and healthcare are among the most salient issues dividing the two major presidential candidates. Yet, there is nothing in the newspaper's analysis that groups voters according to their views on any of these major issues. Nor is there any mention of party identification, which often acts as a catch-all variable for a host of issues.

The variables chosen to classify respondents were 1) respondents' enthusiasm about the election, 2) whether respondents think the election would make a difference to them, 3) respondents' opinions (favorable or unfavorable) of each of the two major candidates, and 4) how certain respondents were to vote for the candidate of their choice. As these variable make clear, the classification scheme focuses almost exclusively on election turnout factors, with no mention of issues. Even the favorability ratings can be considered turnout variables in this context, because voters who are negative about both candidates are least likely to vote, while those who are positive about both candidates are mostly likely to vote. This is not to say that a mostly horserace-driven analysis, as this one is, doesn't provide some insights into the electorate. There are many different angles from which to analyze the electorate, and this is certainly a valid one. To me, it's just not as interesting as one that is more political in context.

Like most political junkies, I find intriguing almost any statistical analysis of polling data that goes beyond the simple marginals, and USA Today should be congratulated for making the effort. Still, I'd like to see a little more politics thrown into the mix - even if only to take these six types and describe their party identification, as well as their responses to other public policy questions. But mostly I would like to see a completely new cluster analysis that included policy attitudes as the defining variables for the groups. This is not to say that issues alone will determine the election. But I don't think we can get a good read on the electorate, and which types of voters will ultimately "decide the election," if we ignore issues altogether.

* The percentages exceed 100 percent because of rounding error.

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