How do I compare polls that sample “all adults” to ones that use “registered voters”?
Q. With the 2012 election approaching, shouldn’t the Pew Research Center now concentrate on conducting opinion surveys among voters, rather than all adults? What do I need to know in comparing an “all adults” to a “registered voters” poll?
The presidential campaign is moving into high gear and many polling organizations are, in fact, conducting surveys only of registered voters, or even in some cases only likely voters. This is not the approach of the Pew Research Center, which studies public attitudes toward politics, the press and policy issues. On subjects ranging from the debt crisis to the war in Afghanistan — issues that affect all Americans, voters and non-voters alike — the Center attempts to get the broadest possible measure of public attitudes.
This is not to say that the Center does not track the electoral preferences of voters. While we ask election questions — indeed, all questions — of the public, we present the results of election questions based on registered voters in our survey reports. Registered voters are adults who say that they are “absolutely certain” they are registered to vote in their precinct or election district (usually around three-quarters of all survey respondents). Typically, the views of registered voters are not very different from those of the general public. Yet on election questions, we feel it is important to present the results based on those who are at least certain they are registered to vote; a person who tells us they are not registered, or is not sure, is very unlikely to cast a ballot. As the election approaches in fall 2012, we will increasingly report on the preferences and attitudes of likely voters as well as registered voters. More detail on how we identify likely voters is available here.
In our July 28 survey report — see “Obama Loses Ground in 2012 Reelection Bid” — 41% of registered voters said they would like to see Obama reelected while 40% said they would prefer that a Republican candidate win the election. The accompanying topline questionnaire shows the responses of all adults — as well as registered voters — on this question: 42% of all adults said they favored Obama’s reelection while 37% preferred a Republican. The slight Obama edge among all adults is not unusual; those who tell us they are not registered to vote include more young adults and minorities — groups that tend to be more supportive of Obama.
On election questions, the Pew Research Center wants to provide an accurate gauge of voter intentions. Yet the Center also has conducted extensive research on non-voters — who they are, what they think, and why they do not vote. For more, see “The Party of Non-Voters” from October 2010 and “Who Votes, Who Doesn’t, and Why” from October 2006.
Carroll Doherty, Associate Director, Pew Research Center for the People & the Press