Excerpt: The latest estimates of telephone coverage by the National Center for Health Statistics found that a quarter of U.S. households have only a cell phone and cannot be reached by a landline telephone. Cell-only adults are demographically and politically different from those who live in landline households; as a result, election polls that rely only on landline samples may be biased. Although some survey organizations now include cell phones in their samples, many -- including virtually all of the automated polls -- do not include interviews with people on their cell phones.
