05/17/2006 - A growing number of Americans rely solely on a cell phone for their telephone service, and many more are considering giving up their landline phones. This trend presents a challenge to public opinion polling, which typically relies on a random sample of the population of landline subscribers. A new study of the issue finds that cell-only Americans - an estimated 7%-9% of the general public - are significantly different in many ways from those reachable on a landline. They are younger, less affluent, less likely to be married or to own their home, and more liberal on many political questions.
Yet despite these differences, the absence of this group from traditional telephone surveys has only a minimal impact on the results. Specifically, the study shows that including cell-only respondents with those interviewed from a standard landline sample, and weighting the resulting combined sample to the full U.S. public demographically, changes the overall results of the poll by no more than one percentage point on any of nine key political questions included in the study.
Estimates of the respondents' likely congressional vote this fall, approval of President Bush, opinion about the decision to go to war in Iraq, and other important social and political measures are unaffected when cell-only respondents are blended into the sample. The relatively small size of the cell-only group, along with the demographic weighting performed when it is combined with the landline sample, accounts for the minimal change in the overall findings.
This research effort was undertaken by the Pew Research Center, in conjunction with the Associated Press and AOL, to assess the challenge posed by cell phones to random digit dial surveys. The project entailed a survey of 1,503 U.S. adults, with 752 interviewed in a conventional landline sample and 751 interviewed on their cell phones, using a sample drawn from a nationally representative cell telephone number database. The interviews were conducted March 8-28, 2006 and averaged about 11 minutes in length. Among those interviewed on their cell phones, 200 (27%) said that their cell phone was their only phone. Details about the survey, including response rates, costs, and other issues, are discussed in the full report.
Read the report The Cell Phone Challenge to Polling on the Pew Research Center for People & the Press Web site.