Relevance & Research Question: Nonresponse in online panel surveys is problematic since it may lead to a bias. An important measure to secure respondent cooperation and the quality of responses is the use of monetary incentives. The purpose of this paper is to find out which incentive strategy is efficient for long term participation of respondents. Efficiency implies both low recruitment costs combined with high response rate after entrance in the panel.
Methods & Data: An experiment was carried out in the LISS panel (Longitudinal Internet Studies for the Social Sciences, an online panel based on a true probability sample of households) in 2007 to determine the optimal recruitment strategy for a new online household panel. The monetary incentives varied during the recruitment. The incentives were either promised or prepaid and the amount varied (10, 20 or 50 euros). More than 500 respondents were randomly selected in the different incentive conditions. This paper takes a different approach to model the time-to-event of nonparticipation: survival analysis. The event in this case is nonparticipation. This method has two important advantages: 1) incorporates the timing of the event and 2) allows for censoring. This research will provide new evidence on the timing of nonparticipation and the influence of different incentive strategies on this timing.
Results: A pilot study was performed to evaluate the effect of the incentive strategies on the recruitment of respondents for the online panel. The highest response rate was found for the lowest prepaid incentive. Section incomplete, see remarks.

Added Value: The willingness of respondents to participate for a long term in the panel for different incentive strategies is an important topic in the literature on survey nonresponse. The innovative aspects of this study are as follows. First, the recruitment incentives are investigated to determine which strategy is optimal for both recruitment and retention of respondents for a longer term. Second, this paper will use a different method of analysis in order to look at the timing of nonparticipation in relation to incentive strategies. This helps us to define an efficient incentive strategy for an online panel.