During the initial survey, face-to-face interviews
are used because probability sampling is not possible online at this time.
During later stages, Internet-based surveys are used to help keep costs down
and increase speed. However, while the Internet penetration rate is high in
Korea, it is not 100%. Other surveys (e.g., LISS in the Netherlands) have
solved this problem by providing Internet access and a device to panel members
without Internet access. However, our budget could not support this kind of
solution. Instead, we provide an alternative way for panel members without
Internet access to answer the survey (phone or face-to-face).