Excluding Cellphones Introduces Statistically Significant Bias in Polls
This is a graph, per the CDC, of the percentage of “cellphone-only” adults in the United States. The fraction, as of the second half of 2009, was 23 percent of all U.S. adults, or 25 percent of all U.S. households. These adults — about a quarter of the population — are simply ignored by many pollsters.
This is not a new problem — in fact, it’s one we’ve written about on several occasions. But it’s continuing to get worse. The percentage of people who have replaced their landlines with cellphones has climbed at a remarkably steady rate. (There may have been an especially large leap from the second half of 2008 to the first half of 2009, when the recession was at its worst and many people were looking for ways to trim household costs.)
Bear in mind that these figures are already somewhat out of date. The fraction could be in the high 20s by the time we get to November. And if the current trends hold, it could be in the mid or high 30s by the time we get to 2012. Nor does the figure include so-called “cellphone-mostly” households, which is when the house has a landline, but rarely or never uses it to receive incoming calls; another 15 percent of the population falls into this category.