How and Why Does the Targeted “Early Bird” Catch the Extra Worm? A Randomized and Controlled Experiment on the Effects of Prepaid and Time-Limited Postpaid Monetary Incentives on Participation in a Panel Study’s Web Survey

Abstract

The aim of this randomized trial in Wave 10 of a long-running panel study was to reveal how and why a combination of an unconditional prepaid and a time-delimited conditional postpaid incentive is useful for enhancing survey participation. This trial was conducted in the context of a panel study that has been running since 2012. The target sample consisted of juveniles born around 1997 and attending public school in the German-speaking cantons of Switzerland. In addition to an unconditional 10 Swiss Francs (CHF) (≈ €10 ≈ US$11) incentive, selected panelists who had either responded late or not at all to the previous year’s panel study were promised an additional cash incentive of CHF 10 or CHF 20 if they completed the survey within a period of seven days. The trial examined how this targeted “Early Bird” monetary incentive (EBMI) affected response rates and waiting times when the amount was equal to or twice the prepayment. Additionally, the trial explored why there is an effect of these incentives. It is assumed that the positive effect is based on the target person’s preference for strong reciprocity. First, the combination of postpaid and prepaid incentives both prompted a faster response and increased the response rate of the treated panelists. Second, despite the provision of an EBMI, relatively few non-participants from the last wave could be persuaded to take part in the current study. Finally, the effect of the incentives was mediated by the panelists’ preference for reciprocity.