WASHINGTON — For the first time, the number of U.S. households opting for only cell phones 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 cell phones, 20 percent of households had only cells during the last half of 2008, according to a Centers for Disease Control and Prevention survey released today. That was an increase of nearly 3 percentage points over the first half of the year, the largest six-month increase since the government started gathering such data in 2003.

The 20 percent of homes with only cell phones compared to 17 percent with landlines but no cells.

That ratio has changed starkly in recent years: In the first six months of 2003, just 3 percent of households were wireless only, while 43 percent stuck to landlines.

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.