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Telephone Survey Integrity Threatened as US Homes Go Wireless Only

Nearly one out of six US homes (15.8%) had only wireless telephones in the second half of 2007, according to preliminary results from the July-December 2007 National Health Interview Survey (NHIS) from the Centers for Disease Control and Prevention (CDC).

Moreover, more than one out of eight American homes (13.1%) received all or nearly all calls on wireless telephones despite having a landline phone in the home, the survey found (via CNN).

Consequently, “the potential for bias due to undercoverage remains a real and growing threat to surveys conducted only on landline telephones,” according to the NHIS.

Other findings issued by the CDC:

• More than 32 million adults - about 14.5% of all adults - lived in households with only wireless telephones; similarly, 14.4% of all children - or more than 10 million of them - lived in households with only wireless phones. Those percentages have remained largely unchanged over the past three years.

• The percentage of adults living in wireless-only households has been steadily increasing:
  • In the last 6 months of 2007, more than one out of every seven adults lived in wireless-only households.
  • One year before that (that is, during the last 6 months of 2006), fewer than one out of every eight adults lived in wireless-only households.
  • And two years before that (that is, during the last 6 months of 2004), only 1 out of every 18 adults lived in wireless-only households.
• Approximately 2.2% of households had no telephone service (neither wireless nor landline); approximately 4 million adults (1.9%) and 1.5 million children (2.1%) lived in these households.

Demographic Differences

• Nearly 6 in 10 adults  (56.9%) living with unrelated roommates lived in households with only wireless telephones - the highest prevalence rate among population subgroups considered.
• Adults renting their home (30.9%) were more likely than adults owning their home (7.3%) to be living in households with only wireless telephones.
• Adults living in the South (17.1%) and Midwest (15.3%) were more likely than adults living in the Northeast (10.0%) to be living in households with only wireless telephones.
• Non-Hispanic white adults (12.9%) were less likely than Hispanic adults (19.3%) or non-Hispanic black adults (18.3%) to be living in households with only wireless telephones.

About the data: In May and December, the Centers for Disease Control and Prevention’s National Center for Health Statistics (NCHS) releases selected estimates of telephone coverage for the civilian noninstitutionalized US population based on data from NHIS, along with comparable estimates from NHIS for the previous 3 years. The estimates are based on in-person interviews. From July through December 2007, household telephone status information was obtained for 13,083 households. These households included 24,514 adults aged 18 years and over and 9,122 children less than 18 years of age. NHIS interviews are conducted continuously throughout the year to collect information on health status, health-related behaviors, and health care utilization.