In recent years, web-push strategies have been developed in cross-sectional mixed-mode surveys to improve response rates and reduce the costs of data collection. However, pushing respondents into the more cost-efficient web mode has rarely been examined in the context of panel surveys. This study evaluates how a web-push intervention affects the willingness of panel members to switch survey modes from mail to web. We tested three web-push strategies in a German probability-based mixed-mode panel by randomly assigning 1,895 panelists of the mail mode to one of three conditions: (1) the web option was offered to panelists concurrently with the paper questionnaire including a promised €10 incentive for completing the survey on the web, (2) the web option was presented sequentially two weeks before sending the paper questionnaire and respondents were also promised an incentive of €10, or (3) same sequential web-first approach as for condition 2, but with a prepaid €10 incentive instead of a promised incentive. The study found that a sequential presentation of the web option significantly increases the web response in a single survey but may not motivate more panelists to switch to the web mode permanently. Contrary to our expectation, offering prepaid incentives neither improves the web response nor the proportion of mode switchers. Overall, all three web-push strategies show the potential to effectively reduce survey costs without causing differences in panel attrition after five consecutive waves. Condition 2, the sequential web-first design combined with a promised incentive was most effective in pushing respondents to switch to the web mode and in reducing costs.

In recent years, several longitudinal studies have transitioned from an interviewer-administered to a mixed-mode design, using the internet as one of the modes of data collection. However, a substantial proportion of panelists are reluctant to participate in web surveys when offered a choice in an ongoing mixed-mode panel. We still know little about the characteristics of panel members that drive them to comply with the request to complete surveys via the internet. This study aims to fill this gap by investigating how internet-related characteristics are linked to the willingness of panelists to switch from the mail mode to the web. We use data from multiple waves of the GESIS Panel, a probability-based mixed-mode panel in Germany ( N = 5734). A web-push intervention motivated 28% of 1364 panelists of the mail mode to complete the survey online in a single wave and 70% of these 380 short-term switchers to switch to the web mode permanently. We measured indicators of internet use, internet skills, and attitudes toward the internet as potential mechanisms of this short-term and long-term mode switching in the two waves before the intervention. Our results suggest that internet use and internet skills affect respondents’ willingness to switch modes in a single wave. For these short-term switchers, however, none of the internet-related characteristics could explain mode switching in the long term. We also present self-reported reasons by panelists for not accepting the offer to switch modes that correspond to these findings. The results of this study can be used to develop effective push-to-web methods for longitudinal mixed-mode surveys.