A monetary gratuity's effect on the return rate (RR) of a mail survey was studied. Half of the surveys mailed to 507 librarians in Arizona included a 1.00 dollar gratuity. The RR was 80% among those receiving the gratuity and 59% among controls. A survey's RR and consequent validity may be improved by including a gratuity. (SLD)

A metanalysis involving 62 studies compared the response rate to mailed surveys with and without a monetary gratuity. The average response rate increased 19% when a gratuity was enclosed. Other findings that substantiate that the external validity of surveys can be increased by gratuities are discussed. (SLD)

The effects of monetary gratuities on response rates to mail surveys have been considered in a number of studies. This meta-analysis examined: (1) the nature of the population surveyed; (2) the effects of gratuities in relation to the number of follow-ups; (3) whether the gratuity was equally effective across different populations; (4) whether the…