Thursday, May 31, 2007

Support for the Death Penalty and Question Wording

One great value of long term data archives for polling information is the ability to compare trends over long spans of time and across different question wording. The Roper Center at the University of Connecticut provides one of these archives. Its subscription only iPoll database includes over 500,000 questions that pollsters have asked since 1935. This is a uniquely valuable resource for opinion research.

Public support for the death penalty over time is a good example of the power of this collection. The plot above looks at death penalty support and opposition since 1936 in Gallup polls. Gallup has maintained a constant question wording over that span giving us the best long term look at this issue. Gallup has a summary of these data on a no-subscription required page here. It provides more data than I look at here.

My point today is two-fold. First, just to look at the trends over time. The standard Gallup question plotted above is
Are you in favor of the death penalty for a person convicted of murder?
Support for the death penalty declined to a low in 1960-75, with support around 50% and opposition around 40% (with some bouncing around a bit.) Following 1975 there was a long growth in support for the death penalty, with support rising to as high as 80% and opposition falling into the teens.

Since the decline in homicide rates in the 1990s, support has declined by about 10 percentage points since 2000, to around 70%, with opposition rising to the mid-20s.

The public overwhelmingly supports "the death penalty for a person convicted of murder."

But now let's consider what happens when we offer a specific alternative to the death penalty. In the classic Gallup question, there is no explicit alternative to the death penalty, so respondents must imagine for themselves what the alternative might be.

Since 1985, Gallup has also asked an alternative question which includes a specific alternative sentence:
If you could choose between the following two approaches, which do you think is the better penalty for murder--the death penalty or life imprisonment, with absolutely no possibility of parole?
This reflects a shift in the policy debate, as no-parole sentences were raised as an alternative to execution.

Presented with this alternative, opinion shifts substantially:

With the "life without parole" option, support for execution falls to just over 50%, while support for life terms rises to the mid 40s. Still a majority in favor of the death penalty, but a substantially more closely divided public than with the classic question.

Two points from this. First, questions define the alternatives respondents are encouraged to consider. The classic question offers one option and leaves it to the respondent to imagine others. The death vs life introduces an explicit alternative, and finds much more support for a penalty short of death. However, we could imagine a question with a third option: life but with a possible parole. Or even specific sentence lengths (10 years? 20? 50?). In part the question reflects the policy debate. But survey questions must also necessarily limit the range of options under consideration. In this, there can be no escape from question wording effects, and no end to argument about whether questions "really" capture all the issues. The fact is every question includes some and excludes other options.

The second point is the political one. If one opposed the death penalty, one might be more likely to find support by arguing forcefully for hard time and no parole rather than arguing against the death penalty in principle.