As of the first half of 2010, 26.6 per cent of American homes had only cellphones – eight times as many as six years ago, and more than the 12.9 per cent of homes with only landlines.

“This difference is expected to grow,” the study said.

Between July 2009 and June 2010, 23.9 per cent of adults and 27.5 per cent of children lived in a wireless-only home, the study said. Arkansas led in wireless-only homes for both adult and children, with 35.2 per cent of Arkansas adults and 46.2 per cent of Arkansas children living in a home without a landline phone.

New Jersey boasted the lowest shares of homes with just a cellphone, tied with Rhode Island with 12.8 per cent of U.S. adults and tied with Connecticut with 12.6 per cent of U.S. children.

This shift has implications for telephone surveys, who for years did not call cellphone numbers. “Best practices for conducting surveys by calling wireless telephones are not yet known,” the study said, “but substantial research has been conducted to address the known operational challenges.”

Work will need to be done to exclude cell numbers in homes where a landline number would be called in a survey to eliminate overlap, the study said.

The clear majority U.S. households now have cellphones, regardless of whether they have a landline or not. Iowa leads the nation in percentage of adults living in cellphone-owning homes, at 91.8 per cent. Utah, Colorado, Kansas, Minnesota and Delaware all exceed 90 per cent.

South Dakota had the lowest percentage of cellphone-owning homes, at 47.9 per cent. Montana was a distant second at 60.6 per cent.

According to the study, 2.0 per cent of American households have no telephone service.