RESPONSE RATES IN SURVEY-RESEARCH - A METAANALYSIS OF THE EFFECTS OF MONETARY GRATUITIES

A meta-analysis was used to compare the response rate to mailed survey s with (E) and without (C) a monetary gratuity. The average response r ate increased 19% when a gratuity was enclosed. When a gratuity was pr omised (contingent on the return of a questionnaire), the average incr ease was 7%. Larger gratuities had a greater effect than lesser amount s-an enclosed $1 gratuity increased the response rate by 20%. This pat tern was consistent regardless of the salience of the topic or the nat ure of the population (general vs. professional) surveyed. The impact of the gratuity remained substantial even when the survey design inclu ded 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 fa iled 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 the use of monetary gratuities.