CONDUCTING PHYSICIAN MAIL SURVEYS ON A LIMITED BUDGET - A RANDOMIZED TRIAL COMPARING 2-DOLLAR-BILL VERSUS 5-DOLLAR-BILL INCENTIVES

OBJECTIVES. The effects of incentive size on physicians' response rate s to a mail survey were determined. METHODS. One thousand US primary c are physicians were assigned randomly to receive a survey with either a $5 bill or a $2 bill as an incentive. For each of the two incentive groups, the overall response rate for three mailing waves, the total c ost, and the total cost per usable response were measured. RESULTS. Th e response rate among those receiving the $5 bill (61%) was 32% higher than the response rate among those receiving the $2 bill (46%); overa ll costs were slightly higher in the $5 group, but the cost per respon se for each group was similar ($15.46 versus $14.93). For the same cos t, a higher response rate could have been achieved in the $2 group if costs saved from foregoing the third mailing were instead used to incr ease the incentive for a portion of the subjects. CONCLUSIONS. A $5 bi ll incentive yielded a higher response rate among the physicians in th is study than did a $2 bill incentive. Moreover, the powerful effect o f the incentive size, combined with the consequent decline in the cost s of subsequent mailing waves, suggests that resources in a fixed surv ey budget are allocated more efficiently to increasing the initial inc entive rather than to providing a third wave to nonresponders.