Mark Blumenthal | February 29, 2008
Topics: 2008 , ABC/Washington Post , ARG , CNN , Disclosure , Divergent Polls , Exit Polls , PPP , Rasmussen , SurveyUSA , Zogby
Last fall, I asked all of the organizations that conducted Iowa Caucus surveys to disclose the demographic composition of their samples and several other aspects of their methodology. Although cooperation was mixed, our "disclosure project" demonstrated how polls that are theoretically reporting on the same population of "likely voters" can sample very different kinds of people.
With so much attention focused on Ohio and Texas this week, I thought it would be worthwhile to attempt a less ambitious version. Earlier this week, I sent all the pollsters that had released surveys in either state in recent weeks to disclose some of their demographic composition and to estimate the percentage of Texas adults that their surveys represent.
While new polls have been appearing every day, I want to report the responses so far, starting with Texas.
The demographic mix is especially important in Texas given the large percentages of both African American and Latino voters there. Fortunately, in this case at least, we now have a fairly complete look at how these polls of "likely Democratic primary voters" differ demographically. When the data was not already in the public domain, I received quick cooperation (in Texas) from the pollsters at Washington Post/ABC News, Constituent Dynamics, Hamilton Campaigns and Public Policy Polling (PPP). Also, an encouraging number of pollsters have included demographic profile data their Texas releases, including several that are typically more reticent, including ARG, Rasmussen Reports. And thanks to the Houston Chronicle, even the Zogby/Reuters/C-SPAN poll helped make the world a "better place" by making cross-tabs featuring demographic composition available on Chron.com.
As in Iowa, the results show considerable variation, particularly on the Latino or Hispanic percentage of the samples, which vary from a low of 24-26% (ARG) to a high of 39% (Post/ABC). Other categories also show wide variation including the percentages of African Americans (from 14% to 23%), women (from 51% to 58%) and voters over 65 years of age (from 15% to 26%
30%; comparisons by age categories are especially difficult, since no two pollsters report exactly the same age breaks [Update: At "Joe's" suggestion, I've added some additional age breaks where available]).
I have included comparable numbers from the 2004 exit poll,* although we will not know what the "right" answer is until the votes are cast and results from this year's exit poll are available.
If they had not yet done so in their public release, I also asked pollsters to estimate the percentage of Texas adults represented by their samples, which is a decent measure of how tightly they screened for likely voters. The percentage of eligible adults that participated in the Texas Democratic presidential primary was just 6% of eligible adults in 2004 and 9% of eligible adults in 2000 (if calculated as a percentage of all adults, including non-citizens, the percentages would be 5% and 8% respectively).
Even though the following table includes results for just four pollsters, the range of adults represented** is huge, from a low of 7-8% for the Texas Credit Union League(TCUL)/Hamilton Campaigns/Public Opinion Strategies poll to a high of 40% on the first poll from SurveyUSA. The TCUL poll obviously comes closest to past turnout, although turnouts have been much higher in other states so far this year than in 2004. The ABC News release concedes that an actual turnout of 24% of adults is "unlikely" but reports that "vote preference results are similar in likely voter models positing much lower turnout."
Next, Ohio... and then after posting all the statistics, I'll come back and speculate about what they might mean for what everyone cares about: where the race stands heading into the final weekend. Given the time crunch, I put these tables together quickly. So if you spot a typo or can help fill in a blank that I've missed please send an email (to questions at pollster dot com).
*UPDATE: All of the 2004 exit poll results in the table above are from the final weighted data available from the Roper Center archives. Some of the percentages differ slightly from those posted on election night 2004 by CNN and still available online. The difference is likely due to final weighting done after 10:43 p.m. on March 9, 2004, the time the CNN tables were last updated. An earlier version of the table posted above was based, in part, on the CNN results.
**For the ABC/Post, CNN and SurveyUSA polls, we estimate the percentage of adults represented by dividing the number of interviews conducted among likely primary voters by the number of adults interviewed. Since those samples of adults will include non-citizens, and since non-citizens are 12% of the Texas adult population, I calculated a range for the two polls -- PPP and TCUL -- that sample from lists of registered voters (see "Update II" of this post for more explanation).
[Table updated on 3/1 to include Below/WFAA/Public Strategies surveys].