The Impact Of 'Cell-Onlys' On Public Opinion Polling

Ways of Coping with a Growing Population Segment

The proportion of Americans who rely solely on a cell phone for their telephone service continues to grow, as does the share who still have a landline phone but do most of their calling on their cell phone. With these changes, there is an increased concern that polls conducted only on landline telephones may not accurately measure public opinion. A new Pew Research Center study finds that, while different demographically, Americans who mostly or exclusively rely on cell phones are not substantially different from the landline population in their basic political attitudes and preferences.

On key political measures such as presidential approval, Iraq policy, presidential primary voter preference, and party affiliation, respondents reached on cell phones hold attitudes that are very similar to those reached on landline telephones. Analysis of two separate nationwide studies shows that including interviews conducted by cell phone does not substantially change any key survey findings.

These findings are based on two surveys of adults, conducted Oct. 17-23 and Dec. 19-30, 2007 by the Pew Research Center for the People & the Press. The surveys included interviews with a total of 2,596 adults reached in a conventional landline sample, as well as 841 adults interviewed on their cell phones, using a sample drawn from a nationally representative cell telephone number database. Of those reached on a cell phone, 312 people (or 37%) reported that their cell phone is their only phone.

When data from both samples are combined and weighted to match the U.S. population on key demographic measures, the results are virtually identical to those from the landline survey alone. Across more than 100 political and attitudinal questions on the surveys, including cell phone interviews does not change the results by more than two points in the vast majority of comparisons, and in only one comparison is the difference as large as 4 points.

In particular, there is no evidence that the polling in the Democratic and Republican nomination contests is biased by the fact that most polls rely only on landline interviews. In the December national poll, support for no candidate in the landline sample changed by more than two points when the preferences of cell phone respondents were blended in. The same was true in the October national poll.

There is no doubt that Americans who rely solely on cell phones differ from the rest of the public in some key respects. However, in most cases these differences are the result of their demographic characteristics, particularly the fact they tend to be very young. Since adjustments for age are made in standard landline surveys, adding the cell-only component to the survey substantially increases the raw number of younger people surveyed, but does not alter the overall weight of younger respondents in the final estimates.

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Source: http://people-press.org/reports/display.php3?ReportID=391