Effect of Small Monetary Incentive and Demographic Characteristics on Response Rate of Self-Administered Questionnaire Mailed to Rural Women.

Objectives: The National Children's Study (NCS) is a longitudinal observational study that will examine the effects of genetics and environment on the health and development of children in the United States. The NCS is in a Vanguard, or pilot phase, so it is important to determine the feasibility, acceptability and cost of different data collection methods. The purpose of this study was to determine whether demographic characteristics differed in self-administered questionnaire (SAQ) completion rates, and to examine response rates when a $2 incentive was included with the mailed questionnaire.

Methods: Subjects for the study (~500) were being followed by a local call center and were mailed SAQs. Women who did not complete their last telephone event were eligible. Women were randomized to receive a $2 bill incentive with their SAQ (approximately 250 women in each group).

Results: Approximately 450 women comprised the final sample. In the incentive group, 35% of SAQs were returned, which was significantly higher than the 27% returned in the non-incentive group (p<0.001). No significant differences in completion rates based on demographic characteristics were seen, except in divorced women. The final cost per completed SAQ was $12.51 in the incentive group compared to $7.57 for the non-incentive group.

Conclusions: Adding a $2 bill as an incentive significantly increased response rates of hard-to-reach rural women completing mailed questionnaires about pregnancy information. Future research should focus on different incentive amounts and types and how they influence response rates.