"If the percentage of adults living in cell-only households continues to grow at the rate it has been growing for the past four years, I have projected that it will exceed 25 percent by the end of 2008," Stephen J. Blumberg, a senior scientist at the National Center for Health Statistics, wrote in an e-mail message.
The American Association for Public Opinion Research has been examining the question and formed a group to study it. The association says it will issue its report early next year.
Paul J. Lavrakas, a survey methodologist and a former professor at Northwestern and Ohio State, has been a driving force behind the research at the association. Mr. Lavrakas said that he could not "imagine how anyone can feel safe in planning their election coverage without including cellphone sampling for the 2008 election."