Response Rates in Survey Research: A Meta-Analysis of the Effects of Monetary Gratuities.
Abstract A meta-analysis was used to compare the response rate to mailed surveys with (E) and without (C) a monetary gratuity. The average response rate increased 19% when a gratuity was enclosed. When a gratuity was promised (contingent on the return of a questionnaire), the average increase was 7%. Larger gratuities had a greater effect than lesser amounts—an enclosed $1 gratuity increased the response rate by 20%. This pattern was consistent regardless of the salience of the topic or the nature of the population (general vs. professional) surveyed. The impact of the gratuity remained substantial even when the survey design included two mailings—the use of follow-ups did not wash out the effect of the gratuity. The impact of the gratuity appeared to be attenuated by poor survey design and instrumentation, such as a cover letter that failed to present the incentive as a gratuity (rather than compensation). The findings indicate that the external validity of mail surveys can be substantially increased by ...