The number of Americans who rely solely or mostly on a cell phone has been growing for several years, posing an increasing likelihood that public opinion polls conducted only by landline telephone will be biased. A new analysis of Pew Research Center pre-election surveys conducted this year finds that support for Republican candidates was significantly higher in samples based only on landlines than in dual frame samples that combined landline and cell phone interviews.
The difference in the margin among likely voters this year is about twice as large as in 2008.
Across three Pew Research polls conducted in fall 2010 -- conducted among 5,216 likely voters, including 1,712 interviewed on cell phones -- the GOP held a lead that was on average 5.1 percentage points larger in the landline sample than in the combined landline and cell phone sample.
In six polls conducted in the fall of 2008, Barack Obama's lead over John McCain was on average 2.4 percentage points smaller in the landline samples than in the combined samples.
Cell phones pose a particular challenge for getting accurate estimates of young people's vote preferences and related political opinions and behavior. Young people are difficult to reach by landline phone, both because many have no landline and because of their lifestyles. In Pew Research Center surveys this year about twice as many interviews with people younger than age 30 are conducted by cell phone than by landline, despite the fact that Pew Research samples include twice as many landlines as cell phones.
According to the latest estimates from the National Center for Health Statistics, in the second half of 2009, 38% of 18 to 24 year olds and 49% of 25 to 29 year olds lived in households that had no landline. And research has shown that people younger than age 30 who are cell phone only can have different behaviors and attitudes than those who are reachable by a landline phone. [emphasis added]
Tuesday, November 23, 2010
Cell Phones, Landlines, and Public Opinion
Our chapter on public opinion and political participation describes the challenges of getting accurate measure of public sentiment. One problem is that a growing number of voters do not have landlines at home, only cellular phones. Pollsters may not use automatic dialers to make calls to cellular phones, so it is most costly to reach them (p. 249). Pollsters may be tempted to save money by skipping cellular phones, but a new Pew study shows that landline-only polls produce distorted results.