Using Dual Frame Samples of Cell and Landline Phones in Spain. Challenges and Outcomes

Technological changes and the rapid adoption by the population of emergent technologies, such as mobile phone, have strongly impacted communicative behavior and uses. In almost one on five Spanish households (one on four following EU e-Communications Households Survey, 2008), cell phones have replaced land lines as the principal long distance communication device. These households present a specific profile differentiating them from those that have both technologies at their disposal, and in greater measure from those that only have a land line. The most important impact of this process for research based on telephone surveys is that, despite the fact that telephone coverage has not ceased to increase until practically becoming universal, more and more homes every day are excluded from the sampling frame of traditional telephone surveys. In the last years we have witnessed a growing concern on this issue and more and more scholars are contributing to this area of research (Kuusela and Simpanen, Callegaro, Vehovar, Fuchs, Buskirk, Steeh, Brick, Keeter, ZuWallack, Fleeman, Lavrakas, etc.). The Institute for Advanced Social Studies (IESA) began to carry out phone interviews in 2003. We started to analyze the impact of this problem in Spain in 2004 as a response to our growing problems locating young respondents (Pasadas del Amo et al. 2004, 2005, 2006, 2007, 2008). In 2007, we conducted our first telephone survey using a dual frame sample of Cell and Landline phones at a national level. In 2008 we also applied this methodology to telephone surveys carried out at a regional level. This methodology has become the standard procedure for the telephone surveys conducted at IESA in 2009. The main aim of this paper is to share our experiences and results with the implementation of dual frame telephone surveys and to contribute to the debate about the best solution for addressing the challenge posed by the growing of the cell-only population. With this objective in mind, first we will outline the main features of phone coverage and the profile of mobile-only households in Spain. Then we will explain our procedures for designing and conducting dual frame telephone surveys. Based on our results, we will finally discuss on the impacts of including cell-phone in telephone surveys samples at two levels: impacts on outcome rates and impacts on surveys estimates.Peer Reviewe