In the SHARE Wave 10 refreshment sample (target number of interviewers: 2000), a randomized 2×2 experiment testing the effectiveness of a 5 euro prepaid incentive and the inclusion of a contact card for the interviewer found that the prepaid incentive was quite effective at increasing response rates (about 6.9 percentage points), while the inclusion of the interviewer-specific contact card was not. The contact card also had no influence on the effect of the incentive.
