Impact of Prepaid Incentives in Face-to-Face Surveys: A Large-Scale Experiment with Postage Stamps

A large-scale experiment embedded in the Dutch Labor Force Survey (LFS) evaluated the effectiveness of prepaid incentives on response rates. Postage stamps were used as a prepaid incentive since sending cash by mail is disallowed in the Netherlands. The survey was mailed to 6,195 addresses without an incentive. A 5-stamp (2 euro value), 10-stamp (4 euro value), & 20-stamp (8 euro value) incentive was included in the mailing to 3,146, 3,148, & 500 addresses respectively. The results showed that including postal stamps generated a substantial increase in responses. The control group response of 65 percent was increased by 5 percent, 8 percent, & 7 percent for letters containing the 5, 10, & 20 stamps respectively. However, incentives did not appear to improve selectivity, had almost no impact on response distributions over different subpopulations, & hardly changed the key characteristics in the LFS. It is concluded that additional research is needed to determine the effect of incentives on selectivity as well as on response bias. Tables, References. J. Lindroth