Panel Attrition and Gratification

(together with Werner Hemsing and Lorenz Gräf, Globalpark AG)

In order to study panel attrition and optimal gratification strategy for survey participation, a study has been carried out at Globalpark AG. A commercial online access panel has been analyzed with regard to drop-out and incentives given to participants. An online access panel is a group of internet users that are invited to participate in surveys on a regular basis. Participants might be recruited both in the world wide web, offline (e.g. by means of CATI), or based on pre-existing databases. The representativity of an online access panel largely depends on the recruiting of the panel members. For surveys, panel members are drawn randomly or by selecting them according to certain characteristics. Consequently, different panel members participate in different surveys.

Figure 1: 699 panel members have been chosen as a reference group. They have been invited to up to twelve projects with different gratification strategies. Four additional surveys in April and Mai 2002 served as a benchmark whether or not the panel members were still active and reacted to invitations.
Figure 1: 699 panel members have been chosen as a reference group. They have been invited to up to twelve projects with different gratification strategies. Four additional surveys in April and Mai 2002 served as a benchmark whether or not the panel members were still active and reacted to invitations.

Within the scope of a study undertaken by the research department of Globalpark AG, the consequences of different gratification strategies and frequency of invitations for surveys on panel attrition has been analyzed.  699 panel members were recruited in August and September 2000 and filled out the initial questionnaire. These panel members habe been surveyed over the next two and a half years up to 12 times. The participants of three of these surveys took part in raffles. Three surveys did not come with any incentive. Six out of the twelve surveys came with bonus points that could be exchanged into shopping vouchers. On average, the 699 panel members have been invited to 6.3 surveys. The average participation rate (answering at least one question) was 61%. In April and May 2002, four surveys had been conducted that again invited the 699 panel members. These four surevys serve as a bench mark whether or not the panel members are still active. 406 panel members reacted to the invitations and answered at least one question. This is equivalent to a participation rate of 58% (see figure 1).

Figure 2: A gratification with bonus points has a positive effect on panel membership. A gratification with raffles contributes to a lower probability of remaining in the panel. Inviting panel members to surveys without any gratification has a negative effect on panel membership.
Figure 2: A gratification with bonus points has a positive effect on panel membership. A gratification with raffles contributes to a lower probability of remaining in the panel. Inviting panel members to surveys without any gratification has a negative effect on panel membership.

Those panel members that remained in the online access panel have been significantly more often gratified by bonus points for their survey participation. The share of invitations to projects without gratification is highest among those who left the panel (see figure 2).

Figure 3: Panel members that left the panel reveived on average less invitations than those who remained in the panel.
Figure 3: Panel members that left the panel reveived on average less invitations than those who remained in the panel.
Figure 4: Panel members that received few invitation, had a higher chance to leave the panel than those receiving many invitations to surveys.
Figure 4: Panel members that received few invitation, had a higher chance to leave the panel than those receiving many invitations to surveys.

Frequent invitations to surveys foster the readiness to remain in the panel. Those panel members that left the panel had been invited to 5.5 surveys on average. Members that remained in the panel, in contrast, had been invited to 7.3 surveys on average (see figure 3). The relation between frequency of invitation and panel attrition is shown in more detail in figure 4. Almost 70% of the panel members that received nine ore more invitations were still active in April and Mai 2002. Conversely, panel members that received only few invitations had a high probability of leaving the panel. 

 

Recommendations:

  • At least three invitations per 6 months for each panelist
  • Refrain from projects without gratifications
  • Survey turnout and gratifications should be planned on the level of the panel members.

 

Hemsing, W., Müller, J. & Gräf, L. (2002). Panel attrition in relation to different kinds of incentives. Presentation at the 5th German Online Research Conference, Hohenheim.


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