According to government statistics released last month, nearly 13% of U.S. households cannot now be reached by the typical telephone survey because they have only a cell phone and no landline telephone, and the share of Americans who are cell-only is increasing rapidly. To monitor this problem, the Pew Research Center conducted four studies in 2006 that included samples of cell phone numbers as well as landline numbers. These studies show that although the cell-only are different from landline respondents in important ways, their inclusion does not change the results of standard landline surveys substantially. Yet while the cell-only problem is currently not biasing polls based on the entire population, it may very well be damaging estimates for certain subgroups in which the use of only a cell phone is more common.

Read full analysis at Pewresearch.org