Do payment incentives affect response time in a social experiment?
Describes a study to test the effect of a monetary reward in mail questionnaire response rates from an ongoing study of 536 families enrolled in the Health Insurance Study. Families were randomly divided into two equal groups. One group received payment with their annual Health Care Questionnaire; the other group was paid only after completing the questionnaire. The purpose of this experiment was to see if prepayment of $5, rather than payment upon completion, would increase the number of early returns. It was found that returns from the prepaid group were significantly greater than those from the postpaid group in the first two weeks, but did not increase early mail returns beyond the initial two-week receipt period. By the third week the difference was insignificant, and there resulted no difference by the fourth week.