A Pew study just released suggests that this year’s presidential polling data could be skewed by as much as 2-3 percentage points, because the polls don’t sample a unique group of potential voters: cell-phone-only users. This could be because people who opt out of landline phone service tend to be lower-income, more transient and in the 30-or-younger age bracket.
The study found that, contrary to a Pew report two years ago, under 30 cell-phone-only respondents trend more heavily Democratic in their political views, than do their landline counterparts.
Combining polls it conducted in August and September, Pew found that of people under age 30 with only cell phones, 62 percent were Democrats and 28 percent Republicans. Among landline users the same age that gap was narrower: 54 percent Democrats, 36 percent GOP.
Similarly, young cell users preferred Democratic presidential candidate Barack Obama over Republican nominee John McCain by 35 percentage points. For young landline users, it was a smaller 13-point Obama edge . . .
. . . According to federal figures, 16 percent of households had only cell phones during the second half of 2007, and another 13 percent had cell phones and landlines but seldom used the landlines to take calls. Cell-only households have been growing by 1 or 2 percentage points every half year.
Typically, pollsters have to weight their polls based on a number of different respondent factors (such as age or political affiliation). But the Pew study shows that the science of polling is still adjusting to the cell phone age.
Interestingly, the issue of including cell phone users could well help to offset the uncertain degree to which the so-called ‘Bradley Effect’ will play. The Bradley Effect is so named for the African American candidate for governor of California who performed significantly worse in his election than the polls had predicted. Pollsters have attributed the discrepency to latent racism; that some voters are unwilling to admit to a pollster their true racial bias, which only manifests itself inside the voting booth. Unfortunately for the Obama campaign, there is no scientific method to determine how much effect the Bradley Effect will have in this election.
On the bright side, the Pew Research Center’s new study could have just found a couple extra percentage points the Obama campaign may desperately need come election day.
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