ESTIMATING THE EFFECT OF INCENTIVES ON MAIL SURVEY RESPONSE RATES - AMETAANALYSIS

This article reports the results of a meta-analysis of 38 experimental and quasi-experimental studies that implemented some form of mail sur vey incentive in order to increase response rates. A total of 74 obser vations or cases were classified into one of four types of incentive g roups: those using prepaid monetary or nonmonetary rewards included wi th the initial survey mailing and those using monetary or nonmonetary rewards as conditional upon the return of the survey. Results were gen erated using an analysis of variance approach. The overall effect size across the 74 observations was reported as low to moderate at d = .24 1. When compared across incentive types, only those surveys that inclu ded rewards (both monetary and nonmonetary) in the initial mailing yie lded 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, respe ctively. There was no evidence of any impact for those incentive types offering rewards contingent upon the return of the survey.