For the first time, the number of U.S. households opting to use a cellphone as their only phone outnumber those that just have traditional landlines in a high-tech shift accelerated by the recession.

In the freshest evidence of the growing appeal of cellphones, 20 per cent of households had only cells during the last half of 2008, according to a Centers for Disease Control and Prevention survey released Wednesday.

That was an increase of nearly three percentage points over the first half of the year, the largest six-month increase since the government started gathering such data in 2003.

The CDC monitors cellphone use in the U.S. because it has an impact on its own health surveys. Other pollsters in turn regularly monitor the results when they are published semi-annually in the CDC national health survey.

The 20 per cent of homes with only cellphones was greater than the 17 per cent of homes with landlines but no cells.

That ratio has changed starkly in recent years. In the first six months of 2003, just three per cent of households were wireless only while 43 per cent stuck to landlines.

Recession pushing move to cellphones: report

Stephen Blumberg, senior scientist at the CDC and an author of the report, attributed the growing number of cell-only households in part to a recession that has forced many families to scour their budgets for savings.

"We do expect that with the recession, we'd see an increase in the prevalence of wireless-only households, above what we might have expected had there been no recession," Blumberg said.

Further underscoring the public's shrinking reliance on landline phones, 15 per cent of households have both landlines and cells but take few or no calls on their landlines, often because they are wired into computers. Combined with wireless-only homes, the results mean 35 per cent of households — more than one in three — are basically reachable only on cells.

The changes are important for pollsters, who for years relied on reaching people on their landline telephones. Growing numbers of surveys now include calls to people on their cells, which is more expensive partly because federal laws forbid pollsters from using computers to place calls to wireless phones.

About a third of people age 18 to 24 live in households with only cellphones, making them far likelier than older people to rely exclusively on cells. The same is true of four in 10 people age 25 to 29.

Those likeliest to live in wireless-only households also include the poor, renters, Hispanics, Southerners, Midwesterners and those living with unrelated adults, such as roommates or unmarried couples.

Six in 10 households have both landline and cellular telephones while one in 50 have no phones at all.

The data is compiled by the National Health Interview Survey, conducted by the CDC. The latest survey involved in-person interviews with members of 12,597 households conducted from last July through December.