In the first half of 2008, 17.5 percent of households were wireless only, up from 13.6 percent a full year earlier, according to the U.S. Centers for Disease Control and Prevention.

The statistics have a margin of error of plus or minus 0.9 percentage point, according to the agency, which collected the data as part of project to determine if national health polls were being skewed by the trend.

Service providers such as Verizon Communications, AT&T Inc, Qwest Communications International and others have seen a steep increase in customers cutting the cord on their home phones.

Qwest said recently that the trend was exacerbated by the weak economy as some customers were disconnecting home phones to save money.

The percentage of households with a landline and a wireless phone declined slightly in the first half of 2008, at about 58.5 percent, compared with 58.9 percent a year earlier.

The figures come from national in-person interviews of approximately 30,000 households per year with at least one adult or child.

The agency concluded that polls were indeed being skewed because they have in the past only called those with traditional landlines. They and other organizations are moving toward incorporating wireless customers into their surveys.

For example, wireless-only households are more likely to contain binge drinkers and smokers, compared with those having landline phones.

Meantime, about 2.5 percent of U.S. households had no phone at all in the first half of the year, compared with about 1.9 percent in 2007, according to the agency.

(By Kim Dixon, Editing by Maureen Bavdek)