Effects of different monetary incentives on the return rate of a national mail survey of physicians

BACKGROUND. Mail surveys of physicians have been characterized by lower res ponse rates than general population surveys, raising concerns about nonresp onse bias. Although monetary incentives have routinely been used to improve survey response among physicians, questions remain regarding how much of a n incentive is most cost-effective. The present study seeks to further exam ine the effects of incentive size on response rates to a national mail surv ey of physicians. METHODS. This study used a random sample of 873 physicians practicing in th e United States; the response rate was 65% (n = 563). Respondents were rand omly assigned to receive a $5, $10, or $20 cash incentive in the initial ma iling. Except for the magnitude of the incentive, the procedures for each c ondition were identical, with each respondent receiving up to 3 follow-up m ailings and 2 telephone calls. RESULTS. Overall response rates ranged from 60.3% for the $5 incentive cate gory to 68.0% for the $10 incentive category. Differences in overall respon se rates across the incentive categories, however, were not significant. Hi gher levels of incentives also did not significantly reduce the number of m ail and/or telephone interventions required to reach the target response ra te of 60.0%. As expected, aggregate costs (excluding labor) were lowest for the $5 incentive group. CONCLUSIONS. Our findings suggest that changes in the magnitude of incentiv e do not automatically result in increases in survey response among physici ans. Possible reasons for this lack of effect as well as alternatives to mo netary incentives are addressed.