Telephone Surveys via Landline and Mobile Phones: Mode Effects and Response Quality

Introduction Telephone surveys play a central role in survey-based research. This becomes clear when considering the widespread use and data quality of telephone surveys (Lepkowski et al. 2008). At the same time, the use of telephone surveys is influenced by social and technological changes. Most prominently, mobile phone technology poses a serious challenge to survey research worldwide (AAPOR 2008, Steeh and Piekarski 2008, Häder and Häder 2009). There is increasing concern that a considerable number of households that are currently supposed to be covered by landline sampling frames can, in fact, not be reached by landline telephone surveys because they rely predominantly on mobile phones (Brick et al. 2006, Keeter et al. 2007). This “mobile-mostly” population currently represents 15 % of adults in United States households. Boyle and Lewis (2009), nevertheless, were able to show that households that consider themselves “mobile-mostly” are still likely to answer their landline telephones. A growing number of mobile phone users have substituted their residential landline telephone for a mobile phone. These so called “mobile-phone-only households” may have implications for the representativeness of telephone surveys, since sampling frames for these surveys have traditionally been limited to landline phone numbers. The non-coverage of households without landline telephones may bias the estimates derived from telephone surveys. Recent studies assume that the number of the mobile-only households is growing worldwide. In Europe this share ranges from 3 % in Sweden to 64 % in the Czech Republic (Häder et al. 2009: 23, European Commission 2008: 31). In the United States these households constitute more than 22 % of households overall (Blumberg and Luke 2009).