Pew Research: the Land-line-less

I heard a snippet on NPR this morning summarizing a report from the Pew Research Center--The Impact Of “Cell-Onlys” On Public Opinion Polling: Ways of Coping with a Growing Population Segment

Being one of those who have ditched the land line in favor of only a mobile phone, I was somewhat interested. Also, many of my friends fall into this category as well. I guess every animal is fascinated by a mirror, eh? According to a Pew 2006 survey roughly 7%-9% of the general public had ditched the land line at that date (see graph above).

Note that I spent my entire time in Canada with a VoIP line, and only ditched it after returning to the US and realizing that I barely used it.

The Pew Research Center was interested because they needed to figure out how badly their polls are skewed by the fact that they couldn't call people with only mobile phones. It is not illegal to poll people on a mobile phone--it is only illegal to use an automated dialer (which makes it a much slower process). Yay!--another reason to ditch the land line.

Of course, this difference would tend to remove younger people from the polling population: As the cell-only population has grown, telephone surveys by Pew and other organizations that rely on landline samples have experienced a sharp decline in the percentage of younger respondents interviewed in their samples. ... This decline is consistent with the fact that the cell-only population is heavily tilted toward young people.

As further detail: Nearly half of the cell-only respondents in the survey (48%) are under age 30. This compares with just 14% in the landline sample (people reached on a landline) and 21% in the population as a whole, according to government statistics. Other characteristics associated with age are also distinctive in the cell-only population. Nearly three-in-ten (29%) cell-only respondents are married, compared with 57% in the landline sample. And only 24% say they own their own home; in the landline sample, 71% do so. The cell-only population also includes a higher proportion of minorities, especially Hispanics (14% vs. 6% among landline users).

However, the 2008 study found that if you control for demographic factors, the replies of the cell phone and non-cell phone populations are close to the same: 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.

...

cell-only Americans are somewhat less likely to rely on newspapers and network evening news for campaign information, but more apt to get campaign news from the internet, late night comedy shows, and to use social networking sites. Not surprisingly, these behaviors are characteristic of younger respondents in general - whether cell-only or not - and the blended results for none of these measures change by no more than two percentage points.

I assume the fraction of mobile-only is going to top out sometime, but I wonder where it will max out.