ESTIMATING THE EFFECT OF INCENTIVES ON MAIL SURVEY RESPONSE RATES - A METAANALYSIS

This article reports the results of a meta-analysis of 38 experimental and quasi-experimental studies that implemented some form of mail survey incentive in order to increase response rates. A total of 74 observations or cases were classified into one of four types of incentive groups: those using prepaid monetary or nonmonetary rewards included with the initial survey mailing and those using monetary or nonmonetary rewards as conditional upon the return of the survey. Results were generated using an analysis of variance approach. The overall effect size across the 74 observations was reported as low to moderate at d = .241. When compared across incentive types, only those surveys that included rewards (both monetary and nonmonetary) in the initial mailing yielded statistically significant estimates of effect size (d = .347, d = .136). The average increase in response rates over control conditions for these types of incentives was 19.1 percent and 7.9 percent, respectively. There was no evidence of any impact for those incentive types offering rewards contingent upon the return of the survey.