Purpose: Lottery-based incentives are being used increasingly to augment response in clinician surveys. Although lotteries may be more convenient and less costly per response than fixed payments, their effects on response rate are uncertain.
Methods: We conducted three randomized trials of fixed payments and actuarially equivalent financial lotteries. In Trial 1, we administered a web-based questionnaire regarding deceased organ donor management to U.S. critical care physicians. Physicians were randomly assigned to a “jackpot lottery” (60%) in which responding would provide a 1 in 1000 chance of winning $5000, to a “high-probability lottery” (20%) in which responding would provide a 1 in 50 chance of winning $250, and to no financial incentive (20%). In Trial 2, we administered identical questionnaires via post to U.S. critical care nurses. Nurses were randomly assigned to a lottery (75%) with a 1 in 400 chance of winning $2000 or to receive an unconditional fixed payment – a $5 bill in the initial outgoing envelope (25%). In Trial 3, we administered a web-based questionnaire regarding consent for blood transfusion to resident physicians. Residents were randomly assigned to a lottery (50%) with a 1 in 250 chance of winning $2500 or to receive a conditional fixed payment – a promise that $10 would be mailed to them after completing the questionnaire (50%).
Results: Among 2,206 eligible physicians in Trial 1, response rates were 30.5% in the jackpot lottery, 31.2% in the high-probability lottery, and 32.4% in the no-incentive group (all p > 0.30). Among 988 eligible nurses in Trial 2, response rates were 39.4% in the lottery group and 58.8% in the unconditional fixed payment group (p < 0.001). Among 758 eligible residents in Trial 3, response rates were 51.1% in the lottery group and 55.8% in the conditional fixed payment group (p = 0.20).
Conclusion: Lotteries appear to have little utility in clinician surveys: they do not improve response rate compared with no incentives and they produce lower response rates than actuarially equivalent fixed payments. The finding that unconditional fixed payments (those provided up front) are superior to lotteries, whereas conditional fixed payments (those provided following response) are not suggests that the ability to introduce a duty of reciprocity, rather than merely guaranteeing reimbursement, is essential for fixed payments to work.
Candidate for the Lee B. Lusted Student Prize Competition