Cell-Phone-Only Samples Up 17.5%

Including cell-phone-only sampling in radio ratings surveys couldn’t be coming at a more opportune time. Preliminary results from the Centers for Disease Control and Prevention’s January-June 2008 National Health Interview Survey found that more than one out of every six American homes (17.5 percent) had only wireless phones during the first half of this year, an increase of 1.7 percentage points from the second half of 2007.

Both Arbitron and new U.S. radio ratings upstart Nielsen plan to include households that only have wireless telephones, beginning with their spring 2009 diary-based surveys.

The most up-to-date estimates from the federal government show the percentages of Americans living in cell-phone-only households to be significantly higher among specific demographics and lifestyles:

— Nearly two-thirds of all adults living with unrelated roommates (63.1 percent).

— One-third of adults renting their homes (33.6 percent).

— More than one in three adults aged 25-29 years (35.7 percent).

— Approximately 31 percent of adults ages 18-24.

— 18 percent of Hispanics.

As age increased from 30 years, the percentage of adults living in households with only wireless phones decreased.

Men (18 percent) were more likely than women (14.4 percent) to be living in homes that had only wireless phones. Additionally, adults living in the South (19.6 percent) and Midwest (17.8 percent) were more likely than adults in the Northeast (9.8 percent) or West (13.7 percent) to live in cell-only households.

Non-Hispanic white adults (14.6 percent) were less likely than Hispanic adults (21.6 percent) or non-Hispanic black adults (18.5 percent) to be living in households only with wireless telephones.

The Telephone Consumer Protection Act of 1991 prohibits placing calls to cell phones with automatic dialing machines — which Arbitron has traditionally relied on to recruit participants for its diary service — unless the caller has a pre-existing relationship with the person being called. To circumvent the law, Arbitron is adding address-based sampling to its existing recruitment methods in 151 markets this spring and in all markets except Puerto Rico in the fall.

Arbitron includes cell-phone-only households in samples for its Portable People Meter electronic ratings service.

Nielsen’s new U.S. radio ratings service, scheduled to launch in the spring in 51 small markets, uses the same address-based sampling methodology the media measurement goliath implemented for its TV measurement service in the November 2008 sweeps. This opens Nielsen’s sample pipeline to landline-less households.